Your next job reference is being written right now by how you act after the manager goes home.

References are written out of unsupervised hours. Anybody behaves well with a manager standing there, so the useful information is what happens at nine at night with two people and a closed door: whether the list still gets done, whether the till is right, whether the phone comes out. That is what gets summarised later into a sentence somebody reads before hiring you.

Decide now what you do when nobody is checking, so you are not deciding it while tired. Finish the list even when it would never be noticed. And ask for the reference while you still work there, because people write better ones when the memory is fresh.