int main()
{
    double a = 12.566789;
    cout << setprecision(2) << fixed << (int)(a * 100) / 100.0 << endl;
    return 0;
}

#include <iostream>
#include <cmath>

int main() {
        std::cout << trunc(3.141516) << std::endl;
}

trunc(a*100)/100

cout << setprecision(2) << fixed << a<< endl;

trunc(a*100)/100

double trunc(double d){ return (d>0) ? floor(d) : ceil(d) ; }

double a = 12.566789;
double b = trunc(a * 100) / 100.0;