A cash register (US English) or till (British English) is a mechanical or electronic device for calculating and recording sales transactions, and an attached cash drawer for storing cash. The cash register also usually prints a receipt for the customer.
In most cases the drawer can be opened only after a sale, except when using special keys, which only senior employees and the owner have. This reduces the risk of employees stealing from the shop owner by not recording a sale and pocketing the money, when a customer does not need a receipt but has to be given change (cash is more easily checked against recorded sales than inventory). In fact, cash registers were first invented for the purpose of eliminating employee theft or embezzlement, and their original name was the Incorruptible Cashier. It has also been suggested that odd pricing came about because by charging odd amounts like 49 or 99 cents, the cashier very probably had to open the till for the penny change and thus announce the sale.