Amazon ALREADY does tax in all states. . .
Not quite.
States where Amazon collects Sales Tax:
http://www.wsj.com/articles/states-that-make-amazon-pay-sales-taxes-1412185657
spoiler: about half of the states.
Due to Amazons treatment of authors, I have shifted my new book purchases to Books A Million, joined their club (which includes free shipping) and pay the Michigan sales tax rather than further support Amazon.