Merchandise sales data processing apparatus

A merchandise sales processing apparatus communicates with a money changer machine for automatically dispensing cash, acquires a sales figure in a transaction, acquires a differential amount in the money changer occurred in the transaction from the money changer, decides if the acquired sales figure matches the acquired price of the fluctuating currency, and acquires a transaction date and time on the transaction if the sales figure does not match the differential amount, and stores the transaction date and time in the memory.