i am not saying that it is your fault ;)
1) i reproduced (thats very funny...) the tax bug.
all is without tax TILL you go to Cart -> Estmate shipping costs -> Apply shipping costs.
Then for all and everything the tax is ADDED.
plz fix that. i ll open a new project, so you can get paid and i can make a feedback, ok?
2) great brit...
Skills: html, mysql administration, php