N.Y. Comp. Codes R. & Regs. tit. 19, § 212.3 – Number and Length of rounds.

(a) A non-championship contest of professional mixed martial arts may not exceed three rounds of five minutes per round with a one minute rest period following each round, unless otherwise directed or authorized in writing by the commission.
(b) A championship contest, or a special event as approved by the commission, of professional mixed martial arts shall be five rounds of five minutes per round with a one minute rest period following each round.
(c) For all contests, a warning bell or other approved auditory device shall sound 10 seconds prior to the start of each round.