It might be OK if everything goes well.
My own experience closing down stores of different types, though, is that that time varies. Most of these places won't let you clock in just a tad early: One place required you be perfectly on time, many others had a 3-minute window before your scheduled time.
Now, if locking the door and leaving took a minute each time (much like employees leaving without locking up), it might not be an issue. But lots of things happen. Sometimes you have to wait for folks to use the toilet: Other times, there are issues with the alarm and you wind up having to call the alarm folks. Sometimes it just takes longer to leave: One fast food place I worked at required folks gather in one vestibule. 2 workers went to their cars, one stopping outside the door and the other stopping at the exit.
This was a security measure in case of a robbery. You were encouraged to clock out once your work was done, though, and wait around for the others and management to get finished as well. You were violating safety standards if you just left.
This was all unpaid time. Even at 5 minutes each day, it adds up. Sure, it ism't the same as requiring hours of unpaid overtime, but that's only due to severity of wage theft. It is like having a lesser punishment for stealing $5 compared to $100.