chelle7272's statement is essentially correct here in the U.S., but in this particular case, as Triple T's link references, the "person" owed was a governmental entity, so was obligated to accept the payment... as seen here:
"... 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.
Since the man is paying a debt (the fine) rather than for services yet to be rendered, it would seem he gets to remit in whichever form of legal tender he desires..."