S.D. Codified Laws § 21-49-34
Such persons may redeem from the purchaser by paying the person making the sale the amount of the purchase price, plus any sums paid by the purchaser to protect his interest in such property in particular, but not in limitation thereof, for such items as taxes, insurance, maintenance expenses reasonably incurred to preserve the value of the mortgaged premises, or payments on a superior lien, together with interest on the total judgment at the same rate of interest as provided in the mortgage. If the purchaser also is the holder of another lien upon the property foreclosed, or part thereof, other than the mortgage upon which sale was made, which additional lien is superior to the lien of the person redeeming, the person redeeming shall likewise pay the amount of such additional lien including interest at the rate provided by the lien or at the legal rate to the date of payment.
SDCL 21-49-34