I imagine that cash registers have the cpu power of at least a cellphone and that they can store transactions over internet in the central company database.
at Tesco scale you really dont want a central database even if its big and high availability. if one store loses connection because of isp issues it would shut down everything and make it impossible to serve customers in that location. a global outage would cost billions. latency is also a big deal when you got a crowd lining up in front of every checkout lane and the self serve machines, at that point it can even turn into a safety/liability issue.
and dont forget that different countries have different rules about customer private data and payment information. if you send eu customer info into the uk for processing you might be breaking privacy laws. some places do automatic tax reporting where you need to send info to a country specific tax office api, get back a code and print it on the receipt.
cash registers dont work alone. its connected with inventory management, employee perf monitoring, payment processing and other things that make more sense as a store local service sending regular reports to corporate instead of waiting for round trips on every operation.
and dont forget that different countries have different rules about customer private data and payment information. if you send eu customer info into the uk for processing you might be breaking privacy laws. some places do automatic tax reporting where you need to send info to a country specific tax office api, get back a code and print it on the receipt.
cash registers dont work alone. its connected with inventory management, employee perf monitoring, payment processing and other things that make more sense as a store local service sending regular reports to corporate instead of waiting for round trips on every operation.