Which of the following is NOT a category of tax-exempt purchasers at auctions?

Retail customers are generally considered end consumers in the market and are typically not classified as tax-exempt purchasers at auctions. In most cases, tax-exempt purchasers are organizations or entities that either have a specific purpose that qualifies them for tax exemption under the law or are engaged in businesses that allow them to avoid certain taxes.

Dealers, for example, are often exempt because they resell the purchased items as part of their business, which means they are not the final end user. Religious organizations are also recognized as tax-exempt under certain regulations due to their nonprofit status and charitable missions. Agricultural purchasers can qualify for tax exemptions as well, especially when acquiring equipment or supplies that support their farming activities.

Thus, retail customers do not fall into these categories and hence do not enjoy the same tax exemptions that are available to organizations or dealers in the auction setting.