Checkers Cash-Tills display faulty!

Checkers Rivonia Village have problems in the cash-out tills, often the display on several tills is not working, so I don't see the price being charged, is this legal? At least very frustrating, I have been complaining to many different store managers and by email to Checkers Headoffice without any response for over 2 years! I will in future go to Supermarkets which work for me, even if they are more expensive!