The city may protect its lien for taxes upon real property by sale at tax sale, or by purchasing the real property at any tax sale or other public sale, or by direct negotiation with the owner. Any such procedure shall be deemed to be for a public purpose. When the city has acquired an interest in real property to protect a tax lien thereon, the owner of any interest in such real property may redeem the same by paying the delinquent city taxes and all accrued charges, penalties, and interest thereon, after the city has held any tax delinquent real property for one year, it may hold the same for public use or sell it at public auction to the highest bidder.