A solution for cs50's "greedy" problem: making change with as few coins as possible

pset 1 greedy

/**
  *
  * greedy.c
  *
  * Peter Downs
  *
  * A program for efficiently making change.
  *
  */
  
#include <cs50.h>
#include <math.h>
#include <stdio.h>

int main(void)
{
    // Declare and initialize a variable and ask for user input.
    float a = 0;
    do
    {
        printf("How much change do we owe you? ");
        a = GetFloat();
    }
    while (a < 0);
    
    // Change to cents and round to the nearest integer.
    int c;
    a = a*100;
        a = roundf(a);
        c = (int)a;
    
    // Declare and initialize variables.
    int counter = 0;
    int quarters = 0;
    int dimes = 0;
    int nickels = 0;
    int pennies = 0;
    
    // Determine number of quarters.
    quarters = c/25;
    
    // Determine number of dimes.
    int d = c%25;
    dimes = d/10;
    
    // Determine number of nickels and pennies.
    int n = d%10;
    nickels = n/5;
    pennies = n%5;
    
    // Sum the number of coins and print answer.
    counter = quarters + dimes + nickels + pennies;
    printf("%d\n", counter);
    
    return 0;
}