I worked in restaurants and I always taught how to count change and not rely on what the register said. If you punch in the wrong amount tendered the change will be wrong, too. Happened at one place I worked and the mindless cashier gave the customer $200 back instead of $20!

It's not hard. Start with the amount due and count up to amount tendered. If you get coin that means the customer wants just dollars back, i.e. $27.32 becomes $27.

I also taught double counting to ensure accuracy. Count it once as you take it out of the register and again as you give it back to the customer. Easy peasy!