Look, someone has scheduled you to (start) work at a specific time, thus to allow another employee to leave, take a break, or that time, they get more business, like late for after work customers that come and buy their dinner
Many times, when you are supposed to get off, then may need another employee to replace you, or they have many customers in line, thus another 5 minutes will get them out, thus then count down your drawer.
And (unless) they are not paying you for (every) minute you work, then it should not matter.
The problem with retail or fast food is that it is not a Monday/Friday job that you work form 8 am to 5 pm, thus the store must have enough employees to take care of the customers and many times that extra 5 minutes could mean keeping customers happy by checking them out vs shutting down and them waiting longer to get checked out.
worked pt years ago in a grocery store