A fast till for a scanner and a queue, with the right VAT on every product and use-by dates kept track of.
A scanner, or the iPad's camera, finds the product by its barcode; several barcodes can belong to one product.
Zero-rated food, reduced and standard rates, set on the category or the product itself.
Batches received with their dates, the soonest sold first, and what must go within the week.
Count, receive and order from suppliers, with what needs reordering listed.
Cash sales carry on with no connection.