Console.WriteLine("enter change");
int change = int.Parse(Console.ReadLine());
int tens = change / 10;
change -= tens * 10; //or change = change % 10
int fives = change / 5;
change -= fives * 5;
int ones = change;
Console.WriteLine("tens: " + tens + ", fives " + fives + ", ones " + ones);
Console.ReadLine();