I've seen tax breakdown signs for gas at some California gas stations (it might be all of them for all I know). I think it would help people figure out how much of the price is taxes and how much of it is something else.

I do also like how Costco breaks down the taxes on liquor, as far as I know those taxes existed before privatization of liquor sales in Washington, its just they were hidden in the "tax in" prices Washington State Liquor stores would post.