So apparently WA state requires you charge sales tax for the customers zip code. I am running version 1.3.9.d and I cant get any of the plug ins that I have found to work for my version. The washington state department of revenue has this

http://dor.wa.gov/Content/FindTaxesA...Interface.aspx

But i don't know if I can get it to work. If anyone can point me in the right direction I will be very grateful.