Design me a the working

I need a product that is to be attached to a trolley in the wholesale stores like Costco and Walmart wherein everything is scattered. This product showed scan the products which are swiped. It should sum up the price of all items. If the buyers enters his budget, the product must compare the items cost and the budget , and then alert the buyer that the the total items in cart are more or less and recommend what to do. If the cash counter is full with rush, there must be an option of swiping the credit card or any card and pay the amount. This info of purchase must got to the respectful shop data be and must print the bill automatically. Please help me