One role per person
Owner, manager, cashier, stock, finance — and, if the shop is a restaurant, floor and kitchen. The person signs in with their own account, not the neighbour's.
What each person is allowed to see
A cashier takes the sale. They do not read wages, and they do not change prices unless you allowed it. The owner sees everything.
The drawer has a name on it
Every sale carries the name of who made it. At close, you know who held the till, not only what is in it.
There is no self-signup. Request a setup and the staff are loaded with the shop.