It's not just the till, either. Here's the guy on the security scanner we went through at the Vatican yesterday:
He isn't actually looking at the screen, it just appears that way from the angle I sneaked my photo from; also, his screen was full, it's an artefact of the photography that only a narrow band shows in the picture.
It's just as well he didn't check his screen, as it happens, as I had my Swiss Army credit card in my bag with a knife in it. I could have knifed a pope if I'd come across one, or hijacked a plane.
Unfortunately, I didn't have my binoculars in my bag, despite having brought them all the way from the UK expressly so I could look at the ceiling of the Sistine chapel with them.