Before calculators and before the computerized cash registers, people actually had to count out change by themselves. Counting backwards ensures the return of accurate change. It is also important to count this way in your own mind when someone is giving you change from a purchase. If you do not know how to give or receive change from a large bill, you will never be sure that you were given the correct amount, or if the other person might have made an error or tried to cheat you. It is not difficult to do, and there is quite an easy and accurate method of counting change out.
When the customer hands you a bill (i.e. $10.00), say to yourself what the purchase price is out of the bill (i.e. $5.22 out of $10.00).
Starting with pennies, count out enough change to get to the next coin or bill size.
Example: $5.22 out of $10.00. Counting out pennies: $5.23... $5.24... $5.25... Counting out quarters: $5.50... $5.75... $6.00...
You will continue giving change for the $10.00 by next using dollar bills. "Counting out dollar bills:" $7.00... $8.00... $9.00... $10.00
If necessary, you will use the next bill size to continue giving change until you reach the bill amount.(i.e. if the bill amount was $5.22 and they gave you $20 to pay).
Practice this by getting a lot of pennies, nickels, dimes and use monopoly money if you do not have bills. Then make believe you are buying for different amounts, and count backwards, until you learn to do this easily and fast.
It is a good idea to place the bill you receive on top of the register or on any surface instead of placing it straight into the till. This might save you from embarrassment or disputes in case you are distracted and forget what the customer gave you.