You don't have to unless you want to, like for security or privacy reasons.
If you want the POS terminal to lock after a transaction then require a code to run a new transaction, go to the Dashboard, select Employees, then set up an employee using the Cashier role (or create a custom role)
The default settings for the Cashier role is to use a Shared POS between multiple employees. This will require the employee to enter their own 4 digit code before accessing the POS.
This is a very common configuration for restaurants, bars, etc., where any waiter/employee can access any available POS terminal.
