After you receive your IRS determination letter, signaling your approval as a non-profit organization, you can apply for state sales tax exemption.

 

Each state has it's own procedures for obtaining sales tax exemption.   Refer to the state sheet in the NOLO book and follow the directions for your state.  This is a simple and self-explanatory process.  Further information can be found in chapter 9, section A of the NOLO book.