How the change is broken down
Change = amount paid − amount due, worked in whole cents so rounding never drifts. The breakdown uses the largest denomination that fits, then repeats with what is left. For US currency this always gives the fewest pieces.
The default set is $100, $50, $20, $10, $5 and $1 bills with quarters, dimes, nickels and pennies. You can include $2 bills, $1 coins and half dollars, or enter your own list for another currency.
Worked example
A customer pays 50.00 for a 13.37 purchase. Change = 36.63: one $20, one $10, one $5, one $1, two quarters, one dime and three pennies, 10 pieces in all.
Other currencies
Enter the denominations as a comma-separated list, for example 20, 10, 5, 2, 1, 0.5, 0.2, 0.1, 0.05, 0.02, 0.01 for euros. Some countries round cash totals to 0.05 or 0.10; round the amount due first when that applies.