Iowa Code § 423.23

Agreements between competing sellers, or the adoption of appropriate rules and regulations by organizations or associations of sellers to provide uniform methods for adding sales or use tax or the average equivalent thereof, and which do not involve price-fixing agreements otherwise unlawful, are expressly authorized and shall be held not in violation of chapter 553 or other antitrust laws of this state. The director shall cooperate with sellers, organizations, or associations in formulating agreements and rules.