Any person violating any of the provisions of this Chapter shall be deemed guilty of a misdemeanor.  Further, the penalty for failure to file a tax return as provided in this Chapter within the time period prescribed by law shall be the greater of $20 or 10% of the unpaid tax due on the return.  Further, if the tax is not paid within the due and payable period as provided in Section 3.15.030 an additional interest penalty on any underpayment, deficiency or delinquency of the payment of the tax shall be paid and computed from the time the original return is due to the date the payment is received. Interest rate shall be calculated on the federal short term rate determined by the Secretary of Treasury under Section 6621 of the Internal Revenue Code and in effect for the preceeding fourth calendar quarter.   (Ord. No. 97-20, Enacted, 11/19/97)