Counting back change is an easy and trustable way to go.

At first, it may seem complicated, but following a few simple steps, we can count the change to customers without any difficulties. First, you will take the customer's money and put it in the cash register. Then, you will have to provide the change from the due amount, and it is good to start with coins and then the bills. For example, a customer buys $32.50 and pays $40. You can put the money in a visible place in the cash register. Then you start by giving two quarters to get to $33, then you give two $1 bills and then a $5 bill, totaling the value in the cash register. Pay attention to every amount of money that goes in or out. Find here an excellent video illustrating how to count back money. Check it out, from 0:33 to 2:04: https://youtu.be/TwWUKQHd6HI

Source: dummies - Counting Change for Customers the Old-Fashioned Way https://www.dummies.com/education/math/counting-change-for-customers-the-old-fashioned-way/

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