Rice by the olonka, fabric by the yard, tomatoes by the pile. Real shops sell in units that never fit a standard price list, and a till has to cope with that without slowing the queue.
Set the unit once
Give each product the unit it sells in and a price per unit. The cashier enters a quantity, the till does the multiplication, and the receipt shows the unit so the customer sees how it was priced.
Keep stock in the same unit
Receive stock in the unit you sell, or in a bulk unit you convert once. Either way the count on the shelf and the count on screen speak the same language.
