The grocery store I worked for, over 20 years ago, did something similar, with similar results. All it did was incentivize locking and unlocking the register as optimally as possible. They also tracked how often and when in the transaction you scanned the customer's loyalty card. It was to the point that basically cashiers who wanted to optimize their numbers wouldn't unlock the register until the customer had their loyalty card in hand.

This is the same grocery store chain that almost failed completely due to a impossible sales requirements in their meat department leading to redating meat and bleaching chicken to increase its shelf life. The company claims they never asked any of their meat departments to do anything like that, they just set impossible standards and held people accountable unless they were able to find a way to cheat.