The establishment, operation or maintenance of stores by the following shall be exempt from the license tax imposed by this article:
(a) The United States of America, this State and its political subdivisions;
(b) Religious and charitable organizations;
(c) Any person or persons engaged within this State in the business of producing agricultural products who, individually or collectively, sell in such store only agricultural products which he or they have produced.
(1973 Code § 13-39)