To the OP
While I am sympathetic to the fact that you do not want to work hours that you are not paid for, most ppl working in corporate America would wish for a job that at most they need to stay 5 – 9 min late on several occasions.
Also, could be this happens to other cashiers as well, it is probably the type of thing that is much easier to notice when it happens to you and not others.
Best of luck whichever way you decide!!