In many states grocery store type food is not taxable. But also, in many states, candy is taxable. But how to define candy? While this seems silly, it's not really that strange when you think about it. The Streamlined Sales Tax Project definition (which several states use) for candy essentially says that if there's flour in the item, it's not candy, it's food. Which means a Kit Kat bar is food, not candy.
Why? Think about the poor clerk at the store. He or she needs an easy way to tell a taxable item from a non-taxable item. Looking at the ingredient list to see if flour is an ingredient is pretty easy.
Personally, I'm pretty excited about Kit Kat bars being "food." I can't wait to tell my nutritionist.
Sales Tax Guy