In any case where property is offered for sale by the commissioner as provided in § 14-316-305 and the sum of the taxes, together with the interest, costs, and penalty, is not bid for the property, the commissioner shall bid therefor, in the name of the district, the whole amount due as aforesaid, and shall execute his deed therefor, as in other cases under this subchapter, conveying the property to the district. All deeds, when executed in conformity with the provisions of this subchapter and recorded, shall be as evidence in all cases showing an indefeasible title in the purchaser, unassailable either at law or in equity.