I would "sell" my business, not sale.  Then, don't you get daily postcards from Accounting Practice Sales and similar companies?  And don't you have a local CPA or accounting/tax chapter where you can advertise?  Or if only a 1040 practice talk to H&R Block or others who want to buy these types of companies?  Or as the game show named it" call a friend".

Look past the Sponsored ads to see several article you can get with the correct wording. 

https://www.google.com/search?q=selling+your+tax+practice&oq=selling+your+tax+practice