S.D. Codified Laws § 5-18C-8
Notwithstanding the provisions of this chapter or chapter 5-18A, 5-18B, or 5-18D, any purchasing agency of a local governmental unit may purchase, without advertising for bids, from a willing vendor, any supplies contained in the state contract list established pursuant to § 5-18D-6, or from any willing vendor at a price at or below that shown in the state contract. The governing body of the purchasing agency shall note in its minutes what supplies were purchased from the state contract and shall further note the identity and address of the vendor and the price paid. If an item is purchased at a price lower than that found on the state contract, the purchasing agency shall note that fact in its minutes and show the identity and address of the vendor and the price paid.
SDCL 5-18C-8