I don’t think you’re necessarily being picked on. I would guess you’ve fallen into the trap of “The better job you do, the more work you get.” You sound like a hard worker who doesn’t like to rock the boat, which is the exact kind of ideal employee toxic bosses love to take advantage of.
Do cafe staff get paid more than store staff or otherwise get additonal benefits?
Your only option really are to sit your boss down and say “Hey, I can’t be the only one being called on to work in the café. If this keeps up I’m going to quit” and then stick to it if it doesn’t change.
If you have the spine for it, you can also just start doing a bad job in the café, but that’s something I don’t think I would be able to pull off either.