Unfortunately, it doesn’t always make a Kiddush Hashem. The cashier may be uncomfortable or aggravated at her mistake being noticed.
I was in Children’s Place and was making some returns and got back too much money. The Rav I asked said I didn’t have to go back, but it would be a Kiddush Hashem. When I went back, the cashier then was under scrutiny of a manager going through the whole receipt, and apparently she made a few mistakes. She certainly wasn’t appreciate that I came back.
So I guess it pays to take into account what your return/correction will cause.