N.J. Stat. Ann. § 54:4-3.69

When real property which is exempted under the provisions of this act is applied to a use other than for conservation or recreation purposes, it shall be subject to taxes, hereinafter referred to as roll-back taxes, in an amount equal to the taxes which would have been payable on such property had it not been exempt, in the current tax year (the year of sale or change in use) and in each of the 2 tax years immediately preceding in which the real property was exempt, with interest compounded at 8% annually; provided, however, that no such roll-back taxes shall be payable when the property is sold, leased, donated or otherwise conveyed to a public agency, nonprofit corporation or organization.