Personally, I feel as though your manager should have planned properly and your colleague should have gone on her break at a time that meant there wouldn't be a situation where no one was there to man the tills. What if you had an urgent appointment to go to? What would she have done then?
If I was on good terms with the manager and it was a one off I'd have stayed the extra few minutes without getting too fussed about it. However I've worked at companies where I've happily stayed late/worked overtime/come in at short notice and instead of appreciating it they still treated me badly because they knew I was easily replaceable.
In short, the probability of me apologising personally depends on the situation. In some jobs I would have absolutely stayed and would have apologised if I had acted the way you did, in other jobs I wouldn't have as it just came down to poor planning on the manager's part, not some unexpected problem that occurred.
Last edited by Sky_Dream; 23-05-2012 at 22:45.