In any county having a purchasing department the board of county commissioners shall appoint a county purchasing agent, who shall be the head of such purchasing department. The county purchasing agent shall have had previous purchasing experience as purchasing agent of a commercial, industrial, institutional, or governmental plant or agency, and shall be placed under such bond as the board may require. The board may establish a central storeroom or storerooms in charge of the county purchasing agent in which supplies and equipment may be stored and issued upon proper requisition by department heads. The purchasing agent shall be responsible for maintaining perpetual inventories of supplies and equipment and shall at least yearly, or oftener when so required by the board, report to the county commissioners a balancing of the inventory record with the actual amount of supplies or equipment on hand.