N.J. Stat. § 18A:18A-24
There may be required from any person bidding on any contract, advertised in accordance with law, that the bid be accompanied by a guarantee payable to the board of education that, if the contract is awarded to the bidder, the bidder will enter into a contract therefor and will furnish any performance bond or other security required as a guarantee or indemnification. The guarantee shall be in the amount of 10% of the bid, but not in excess of $20,000.00, except as otherwise provided herein, and may be given, at the option of the bidder, by certified check, cashier's check or bid bond. In the event that any law or regulation of the United States imposes any condition upon the awarding of a monetary grant to any board of education, which condition requires the depositing of a guarantee in an amount other than 10% of the bid or in excess of $20,000.00, the provisions of this section shall not apply and the requirements of the law or regulation of the United States shall govern.
N.J.S. § 18A:18A-24