[bloodorange]

I genuinely can't tell if you are being serious. If you are being serious, then how do you account for the behaviour of the customer possibly changing based on how the price is displayed (i.e including or excluding taxes etc.)

[bluGill]

Since in the US tax is traditionally never included in any state (exception: gasoline is always advertised with all tax), consumers are not changing behavior. I suspect there are a few who split purchases knowing the above, but for the most part few people do.

Also, you seem to be putting more thought into this than our government has.