BTW on these photos they both have cash registers with memory (they have to, by the law).
On the first photo you can see it partly on the very left.

The other question is why they use an abacus instead of an electric calculator.
I read somewhere that people who are used to it can make calculations using an abacus faster than you can press buttons on a calculator :)

Of course, younger people don't know how to use this ancient device :)