Except as otherwise provided by ordinance under § 58.1-3916, any person failing to pay any county, town and city levies on or before December 5 shall incur a penalty thereon of five percent, which shall be added to the amount of taxes or levies due from such taxpayer, and which, when collected by the treasurer, shall be accounted for in his settlements. No penalty shall be imposed for failure to pay any tax if such failure was not the fault of the taxpayer.