If ASDA was hit?
It depends, if the checkout/EPOS system was taken down, how could they process the transaction? In the old days, every item of stock was labelled with a price. Or prices were memorised, Kwik Save staff had to learn all the prices. Until more recently Aldi and Lidl were still manual, but now everything relies on bar codes and the computer system. The prices are on the shelf labels, and in the computer, but not on the item for sale. As such they could not even pull out a calculator and work out your bill. Even if they could, they would not. Because there is no longer any manual stock and order system. If they don't know what they have sold, how can they replenish stock?
In addition to this, so many traders are not using cash as much, and so the cash office in most stores could not handle the volumes of cash that they used to. Neither could companies like Securicor, that used to do all the cash collections/deliveries, switch back to how they worked before debit cards. Turnover in an out of town store is probably in the region of a million pounds per week, and that is a shed load of cash to handle. I can feel a new wave of scalawagary coming on.