I live in WA and have a state sales tax exemption card for my business.  It allows me to by-pass state sales tax on anything purchased and directly used in my business.   The idea being - I will charge state sales tax on anything I sell from my business.  The state will get their $$$$ in this manner.
I seriously considered utilizing this feature when buying my Kubota and various implements.   However, upon reflection - I didn't want to get sideways with the state tax dept and have a long running battle on this issue.   I bit the bullet and paid state sales tax on everything.
Am I a weenie, woosh - perhaps on this matter.  But consider this - the state has a whole lot more money to fight a potential suit, in court, than I ever will.
Besides - I'd rather go with the flow than have to paddle upstream in this area.