The Washington Department of Revenue has launched a statewide effort to collect sales tax from medical marijuana dispensaries - even as some prosecutors and the Health Department maintain such dispensaries are illegal. Spokesman Mike Gowrylow said that the Revenue Department mailed letters to 90 dispensaries and related organizations on Friday, insisting that medical marijuana is not exempt from state sales tax and that dispensaries must collect that money and turn it over to the state. The letter said dispensaries must also pay the state business and occupation tax.