Let me first preface this by saying that I live in Georgia (I feel that might be mildly important to the conversation), and the problem is not one that I am facing directly but rather one that my girlfriend is facing at her new job.
So my girlfriend (who I am just going to refer to as meg for the sake of convenience) recently got hired at a retail store in the area, and she told me that they are required to stay and do some small tasks after they have already clocked out, that didn't sound right to me, so I decided to ask a little further and this is essentially what she told me:
They get to work and have to do a temperature check before they clock in (seemed pretty standard, especially in these times), then they do their jobs, take their break (they only get one the way the managers schedule them, kind of scummy, but not illegal) and finally when it's time to close, they all go to the backroom together and clock out at the same time. After they clock out then they are aloud to get their stuff from their lockers, and after that they all have to exit the store together (in order to prevent stealing), and this all sounds fine and good, until she told me that if their manager or supervisor see's something that needs to be done, they have to do it before they can leave (puting carts away, wiping a counter off, putting up something tha, etc.). After they have all left the store and the manager/supervisor has locked the doors and armed the alarm, they have to wait there for 5-10 minutes until they hear confirmation that the alarm has been armed, then they can leave.
The time they spend working or having to stay off the clock is minimal, it's still there, and they are not allowed to leave until it has been completed, and I didn't know if this was illegal, and if it was illegal what we could do about it?

