Answer
The installation of new cash register, will improve internal control. A cash sale is rung-up on a cash register with the amount clearly visible to the customer.
Work Step by Step
This will prevent the cashier to receive correct amount from the customer and record less to put in the pocket the difference. Further the customer receives itemized cash register receipt slip and expected to count the balance. The cash register tape is locked and can be viewed / accounted / checked by the supervisors. The receipt cashier does not have any accesses to the tape.
