The Mayor and Councilmembers shall not be excused from voting except upon matters involving the consideration of their own official conduct or in such matters as they may have a conflict of interest as set forth by statute. In all other cases, a vote of aye or nay must be cast. Should the Mayor or Councilmember fail to vote, such vote shall be counted with the majority vote on the issue, and in case of a tie vote, such vote shall be counted as a nay vote.