There was a mom and pop store that was busted a couple of years ago in north Tulsa for doing it. IIRC, they were selling tobacco and beer by ringing up food items.
Back in 1986 when I got my first job at a grocery store, we had a cashier get busted for doing the same thing. Back then it was easier because they used paper food stamps.
I cashiered at a locally owned grocer back in the days of paper food stamps in the 90s, but it never crossed my mind to ring stuff up that way. What was in it for me?
I guess a owner-operated place like the corner store you mention has more incentive and ability.