My Bad... [Week 5 Question]

There has been a few times when I have messed up while working with the cash register. Most of the time I just do something simple that messes me up like a hit the wrong button or enter the wrong amount. But I have mastered fixing it because Ive done it so many times. The only thing that is kinda hard is remembering to do a refund after I mess up because I usually get busy doing something else. Im pretty sure there will be many times when i mess up with the register because lets face it... Im not an expert cash register worker.