Ahhhh, so THAT explains it! Every time I go to Taco Bell, I say "No tomatoes!" And, they always put tomatoes on my food. I just pick them off. I didn't realize they did that to avoid a 5 cent deduction on their pay.
OP, That ^^ is exactly what would happen with such a policy. And, people would start complaining. And, Taco Bell headquarters would wonder why so many people complained about their food being made wrong in a certain area... and all it would take is one worker to mention this policy and the policy would be stopped in its tracks.
edit: I'm not saying whether the policy is legal or illegal. But it's a stupid policy. I certainly wouldn't eat again at a restaurant when I found out they intentionally made my food wrong to avoid having their pay docked. And, once they start doing it intentionally, that opens them up for all sorts of trouble - what happens when the child who's allergic to an ingredient orders something with none of that ingredient?? Lawsuit! That's not to say that this policy couldn't exist either; there are plenty of idiots running businesses out there. However, this policy couldn't possibly last very long without driving customers away for various reasons (either employees are going to be irate when someone causes them to lose pay, else employees are just going to ignore what the customer wanted - that's the nature of such a system.)