According to Nonprofit Organizations (PDF dated March 2009) published by the Washington State Department of Revenue, if you sell items or services as a short-term sale to further the goals of EUUC, you do not need to collect sales tax. Ongoing sales, such as the Bookstore, do collect sales tax. Specifically, Nonprofit Organizations says,
Nonprofit organizations who conduct periodic fundraising activities, which do not constitute the operation of a regular place of business, are exempt from the Business and Occupation (B&O) tax and the requirement to collect sales tax. Fundraising activities include directly soliciting money or other property, or selling goods or services to further the nonprofit organization’s goals. It does not include a regular place of business with regular hours such as a bookstore, thrift shop, restaurant or similar business.
The March 2009 issue of Nonprofit Organizations was current in October 2010. As you plan a sales project, please check the Washington State Department of Revenue for revisioins in the law. As you read, you will need to know that EUUC is exempt from federal tax under Section 501 (c)(3) of the federal internal revenue code.