[CalChris]

It isn't a tax. It's a minimum price. The money goes to the grocer.

  The bill also required a 10 cent minimum
  charge for recycled paper bags, reusable
  plastic bags, and compostable bags ...

http://www.ncsl.org/research/environment-and-natural-resourc...

[ZeroGravitas]

It the UK most shops donate it to charity.