This was my immediate thought too but now they have weighted checkout counters and cameras checking items, but it definitely would have been great in the early days when I used to scan everything up as unwashed potatos
Here the checkout locks down and keeps repeating "unexpected item in the bagging area" and needs an employee to come and check and swipe their card to unlock. I assume the camera system works the same if the colour, shape or size of an item doesn't match
They just read the dark lines for a few bits of data (it's literally just a number). If you're pale enough and the tat done well enough, it should work, assuming the UPC is in the system for the POS scanning it.