I lived in the USSR when self-service supermarkets were just starting up and had automatic tills, a totally new experience for shoppers and for the cashiers.
The cashiers were very suspicious of the tills and used to double check the till total with their abacus.
I would really love to take my ancient old Soviet abacus to the supermarket and push a few of the counters backwards and forwards to 'double check' the till total.
I don't know how to use it, but no matter.
Can you imagine the reaction?