Store manager says we can’t leave until department is spotless and all tasks are completed

I feel like this isn’t legal. SM decided in today’s morning meeting that no associate is allowed to clock out until all tasks given for the day are completed and the area is spotless. I am scheduled a certain time because I have a second job and need to leave then, and when I am given 16 hours of work for an 8 hour shift, no way i’m completing it. Is this legal? does anyone else’s store manager say this?

EDIT: Didn’t realize how many of you are so angry about me having a second job and didn’t realize i’d have to explain it. My second job is taking care of very elderly family members who barely know who they are. I have a letter of exception from corporate that i worked months to get, yes the store manager knows, yes it’s in my file, and no, he doesn’t care and has told me he doesn’t.