S.D. Codified Laws § 10-63-6
A noncollecting retailer may not state or display or imply that no tax is due on any South Dakota purchase unless the display is accompanied by the notice required by § 10-63-2 each time the display appears. If a summary of the transaction includes a line designated "sales tax" and shows the amount of sales tax as zero, this constitutes a display implying that no tax is due on the purchase. This display shall be accompanied by the notice required by § 10-63-2 each time it appears.
Notwithstanding the limitation in this section, if a noncollecting retailer knows that a purchase is exempt from South Dakota tax pursuant to South Dakota law, the noncollecting retailer may display or indicate that no sales or use tax is due even if the display is not accompanied by the notice required by § 10-63-2.
SDCL 10-63-6