The City Council shall lay a tax not exceeding 300 cents on the dollar of the grand list of said City on the ratable estate within the same, whether of residents or nonresidents, for any of the purposes hereinbefore mentioned, and shall make out a rate bill accordingly and deliver the same to the Treasurer and the Constable or Collector shall have power to collect it and may sell property to satisfy the same, and for want thereof may commit any person against whom he or she has such a tax to jail. Such sales for taxes shall be advertised and conducted as provided by the Public Laws; provided however, that, if any parcel of real estate so advertised and sold shall yield a larger amount at such sale than the total amount of taxes, costs, and charges against the owner, such sale shall not thereby be void, but shall stand, subject to the statutory right of redemption, upon tender of payment to the owner of the amount of such excess. And the City Council shall be a Board for the Abatement of Taxes.