It shall be lawful for said City of Dunbar to issue and sell its bonds as provided in this Charter for the sale of other bonds, to pay the City's part of the cost of said improvements as required by this Charter, and it may levy taxes in addition to all other taxes authorized by law, to pay such bonds and interest thereon, provided, that the total indebtedness of the City for all purposes shall not exceed five per centum of the total value of all taxable property therein.