Here is the completed code for this problem. Comments are included, go through it, learn how things work and let me know if you have any doubts. Thanks

// Coin.h

#ifndef coin_h

#define coin_h

#include<stdlib.h>

#include<time.h>

#include<iostream>

using namespace std;

//Coin class

class Coin{

              //required variable to store coin's side

              string sideUp;

              public:

              //public method prototypes

              Coin();

              void toss();

              string getSideUp();

};

#endif

//Coin.cpp

#include "coin.h"

//implementation of all methods

Coin::Coin(){

              //tossing the coin

              toss();

}

//this method will toss the coin, update sideUp variable

void Coin::toss(){

              //generating a random number (0 or 1)

              int i=rand()%2;

              //if i is 0, setting sideUp as heads, or else tails

              if(i==0){

                             sideUp="heads";

              }else{

                             sideUp="tails";

              }

}

string Coin::getSideUp(){

              return sideUp;

}

//200_assign3.cpp

#include "coin.h"

#include<iomanip>

int main(){

              //seeding random number generator

              srand(time(NULL));

              //initializing variables

              double playerBalance=0,computerBalance=0;

              Coin quarter, dime, nickel; //denoting each type of coins

              int round=1;

              bool gameOver=false; //loop controller

              //setting decimal point precision to 2

              cout<<setprecision(2)<<fixed;

              //displaying starting balance

              cout<<"Your starting balance : $"<<playerBalance<<endl;

              cout<<"The Computer's starting balance : $"<<computerBalance<<endl;

              //looping until game is over

              while(!gameOver){

                             //tossing three coins

                             quarter.toss();

                             dime.toss();

                             nickel.toss();

                             //updating player's balance if a coin draw heads

                             if(quarter.getSideUp()=="heads"){

                                           playerBalance+=0.25;

                             }

                             if(dime.getSideUp()=="heads"){

                                           playerBalance+=0.10;

                             }

                             if(nickel.getSideUp()=="heads"){

                                           playerBalance+=0.05;

                             }

                             //tossing three coins again

                             quarter.toss();

                             dime.toss();

                             nickel.toss();

                             //updating computer's balance if a coin draw heads

                             if(quarter.getSideUp()=="heads"){

                                           computerBalance+=0.25;

                             }

                             if(dime.getSideUp()=="heads"){

                                           computerBalance+=0.10;

                             }

                             if(nickel.getSideUp()=="heads"){

                                           computerBalance+=0.05;

                             }

                             //displaying balance after this round

                             cout<<"Your balance after round "<<round<<": $"<<playerBalance<<endl;

                             cout<<"The Computer's balance after round "<<round<<": $"<<computerBalance<<endl;

                             //checking if any of them has won

                             if(playerBalance>=1 || computerBalance>=1){

                                           //game is over

                                           gameOver=true;

                             }

                             round++;

              }

              //displaying ending balance

              cout<<"Your ending balance : $"<<playerBalance<<endl;

              cout<<"The Computer's ending balance : $"<<computerBalance<<endl;

              //identifying the winner

              if(playerBalance==computerBalance){

                             //tie

                             cout<<"Tie! Nobody wins"<<endl;

              }else if(playerBalance>computerBalance){

                             //player

                             cout<<"Congratulations! You won"<<endl;

              }else{

                             //computer

                             cout<<"Sorry! The computer won"<<endl;

              }



}

//OUTPUT (multiple runs)

Your starting balance : $0.00

The Computer's starting balance : $0.00

Your balance after round 1: $0.30

The Computer's balance after round 1: $0.00

Your balance after round 2: $0.35

The Computer's balance after round 2: $0.35

Your balance after round 3: $0.75

The Computer's balance after round 3: $0.45

Your balance after round 4: $0.80

The Computer's balance after round 4: $0.80

Your balance after round 5: $1.20

The Computer's balance after round 5: $1.20

Your ending balance : $1.20

The Computer's ending balance : $1.20

Congratulations! You won

Your starting balance : $0.00

The Computer's starting balance : $0.00

Your balance after round 1: $0.00

The Computer's balance after round 1: $0.10

Your balance after round 2: $0.15

The Computer's balance after round 2: $0.10

Your balance after round 3: $0.25

The Computer's balance after round 3: $0.40

Your balance after round 4: $0.55

The Computer's balance after round 4: $0.80

Your balance after round 5: $0.90

The Computer's balance after round 5: $1.20

Your ending balance : $0.90

The Computer's ending balance : $1.20

Sorry! The computer won

Your starting balance : $0.00

The Computer's starting balance : $0.00

Your balance after round 1: $0.40

The Computer's balance after round 1: $0.40

Your balance after round 2: $0.55

The Computer's balance after round 2: $0.40

Your balance after round 3: $0.70

The Computer's balance after round 3: $0.70

Your balance after round 4: $0.85

The Computer's balance after round 4: $0.95

Your balance after round 5: $1.00

The Computer's balance after round 5: $1.00

Your ending balance : $1.00

The Computer's ending balance : $1.00

Tie! Nobody wins