From http://www.federalreserve.gov/generalinfo/faq/faqcur.htm : According to the "Legal Tender Statute" (section 5103 of title 31 of the U.S. Code), "United States coins and currency (including Federal Reserve notes and circulating notes of Federal Reserve banks and national banks) are legal tender for all debts, public charges, taxes, and dues." This means that all U.S. money, as identified above, when tendered to a creditor legally satisfies a debt to the extent of the amount (face value) tendered.
However, no federal law mandates that a person or an organization must accept currency or coins as payment for goods or services not yet provided. For example, a bus line may prohibit payment of fares in pennies or dollar bills.
Some movie theaters, convenience stores and gas stations as a matter of policy may refuse to accept currency of a large denomination, such as notes above $20, and as long as notice is posted and a transaction giving rise to a debt has not already been completed, these organizations have not violated the legal tender law.
(I wouldn't think the DMV qualifies as a person or organization.)