alt Hacker NewsSame experience here. The one "monitor" employee is busy nearly full time helping out with some issue some customer is having, such that they simply can't be monitoring that everyone's items are ringing up as the actual item instead of "bananas".
But every terminal also has a spycam hanging above it to either "give the appearance" of a big-brother overlord watching to encourage honesty, or is recording everything so that someone can review footage later if some issue is discovered.
Depending on the store those cameras are definitely processing the feed locally to flag shady stuff. I've had a few times I've done something "odd" (not stealing anything but definitely not the normal flow of scan a single item and put in a bag) and have had those systems freak out on me, and the only part of it being weird it would have known was the camera feed.