I had a friend that managed a school cafeteria. They did a brisk lunch time business. They had 3 cashiers. Diners pushed their trays to the register. Everything was ala carte. So each item selected got rung up separately.
1 of the cashier's register was always had the lowest total. But customers were randomly selecting their cashier. The manager found scrap paper in this cashier's waste paper basket that looked like a bunch of tick marks one day. When this cashier was out for whatever reason, on average, the lunch dollar amounts were higher.
It was also mentioned that this person seemed to live beyond their pay. Disneyland every year for vacation, complete with a flight that included a limo ride to the airport. But no hard proof of any theft. At the end of the year, the manager just didn't rehire this particular worker for the next school year.
Daily skim was estimated to be around $100 buck a shift.
I worked with a girl that use to be a cashier in the commissary. Back in the days before electronic scanners. She let a bunch of stuff through that didn't get rung up for certain friends. Later the friends would toss her a few bucks. She didn't see the harm in ripping off the government a couple of times a week.
Yes, employees have been stealing from their employers forever. I think it's harder to do today. But someone will always find a way around the system.