N.H. Rev. Stat. Ann. § 618:9

Whenever a person is committed to a county correctional facility in default of payment of a fine imposed by a justice of a superior court or a district court, he or she shall be discharged from custody by the superintendent thereof at the expiration of a number of days after the date of his or her commitment equal to one day for each $150 of the fine so imposed. The superintendent shall keep a record of all discharges made under the provisions of this section.