double balance = payment - price;

int dollars = (int)balance; // Cut the decimals
int cents   = balance * 100.0 - dollars; //Maybe Java has a fpart() function or something that could work better, I don't know

bill20 = dollars / 20; 

dollars -= bill20 * 20; //Remove the dollars we counted

bill10 = dollars / 10;

dollars -= bill10 * 10;

// ...
//Repeat for each bills, and when you arrive at the cents, repeat the same process starting with 'cents' instead of 'dollars'

   //Array of currency denominations, from largest to smallest (in pennies)
   int Denom[] = {2000, 1000, 500, 100, 25, 10, 5, 1};

   //Display text for plural amounts
   char *DenomStrPl[] = {"$20 bills", "$10 bills", "$5 bills", "$1 bills", "quarters", "dimes", "nickels", "pennies"};

   //Display text for singular amounts (woohoo, fancy stuff)
   char *DenomStrSi[] = {"$20 bill", "$10 bill", "$5 bill", "$1 bill", "quarter", "dime", "nickel", "penny"};

   //Note: all 3 arrays should line up with corresponding values

   int count = 0;     //Number of counts for each current denomination of money
   int curindex = 0;  //Index of the starting denomination type

   //Substitute whatever amount here, and convert it to pennies.
   //Overall this is a pretty bad way of doing it, it won't work for all decimal values.
   double price = 36.41;
   int amount = (int) ceil(price * 100);

   //Just a quick display to see if the value was converted properly
   //If you do any conversions, you might want to output something
   //like this just to make sure it worked.
   printf("$%g = %d pennies \n", price, amount);
   
   //If it checks (amount > 0) then it won't output the final penny count
   while (amount >= 0)
   {
      if(amount >= Denom[curindex])
      {
         //The current amount contains enough money for that denomination, so subtract
         //it from the remaining value and increment the counter
         amount -= Denom[curindex];
         count++;
      }
      else
      {
         //Amount left is less than the current denomination requires

         //If the count is only one, output the singular text.
         //If greater than 1, output the plural text.
         //If zero, nothing will be printed
         if(count == 1)
            printf("%d %s (%d pennies left)\n", count, DenomStrSi[curindex], amount);
         else if (count > 1)
            printf("%d %s (%d pennies left)\n", count, DenomStrPl[curindex], amount);

         //Increment the index to the next size denomination, and reset
         //the count for a fresh start.
         curindex++;
         count = 0;
      }
   }

$36.41 = 3641 pennies
1 $20 bill (1641 pennies left)
1 $10 bill (641 pennies left)
1 $5 bill (141 pennies left)
1 $1 bill (41 pennies left)
1 quarter (16 pennies left)
1 dime (6 pennies left)
1 nickel (1 pennies left)
1 penny (0 pennies left)