ARMA International and all chapters/regions are classified by the IRS as 501(c)(6) not-for-profit organizations; as such, they are liable for paying state/local sales tax. ARMA is NOT considered a non-profit organization, which would be exempt from paying sales tax on any purchases (for example: Red Cross is a non-profit thus do not have to pay sales tax as well as the AIEF).
Not-for-profit organizations primary goal is to fulfill the needs of its members, rather than produce profits for owner/investors. It does not mean the organization should not make a profit. It can and should produce a surplus of revenues over expenses – the surpluses must be used to enhance the position of the organization and its mission.