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.

Sure but while we're at it, let's also break out things like wholesale costs, manufacturing marginal unit cost, per-unit profits, etc. Shed some light on what every layer is getting rather than being distracted by focusing on only a single one.

And of course none of this is incompatible with still printing one big-print all-inclusive price.

People vote on taxes.

That's actually a reason for why it's less useful to show the taxes at the point of sale, as it means people either voted on it or they don't care.

The taxes are on the companies, not the people. If the companies want to pass it along to the people while swimming in record profits, instead of paying with some of those record profits, as the people want and intend: then yes, that makes them greedy.