Any person subject to the provisions of this division willfully refusing to make the reports herein required, or who shall refuse to permit the examination of his records by the Department of Revenue, or its duly authorized agents, shall be guilty of a misdemeanor, and upon conviction shall be fined not less than $50 nor more than $500 for each offense, and in addition may be imprisoned in the county jail for a period not to exceed six months. Each month of failure to make such reports shall constitute a separate offense, and each refusal of a written demand of the department to examine, inspect or audit such records shall constitute a separate offense.