A transaction processing system including a sensing device, one or more cameras, and a processor. The sensing device is configured to detect displacement of a commodity item from a commodity display section. The one or more cameras are configured to capture images around the commodity display section. The processor is configured to track a location of each of one or more customers who is determined to have entered a first area around the commodity display section based on the captured images, and upon detection of the displacement of the commodity item by the sensing device, perform an operation to determine a purchasing customer of the commodity item based on the tracked location of each of the one or more customers, and cause purchase registration of the commodity item in association with an ID of the purchasing customer.