Niners' rhymes with:
niners, decliners, designer's, designers, designers', dinars, diners, liner's, liners, liners', meiners, miner's, miners, miners', minors, niners, refiner's, refiners, refiners', reiner's, reiners, shriners, signers, steiner's, whiners
Niners' sounds like:
narazaki, narc, narciso, narcisse, narcissus, narco, narcos, nares, narjes, narrows, nars, nawrocki, nears, nemmers, nemours, neorx, nerco, nerice, nero's, neuroses, neurosis, new-years, new-york, new-york's, newark, newark's, newmark, niners, niriko, noirs, nomura's, nora's, norcia, norco, noreco, noreiga, norex, norge, norick, noriega, noriega's, noriegas, nork, norkus, norris, norris's, norse, norsk, norske, norway's, norwich, nourish, nourishes, nourse, numeric, numerica, numerous, nurock, nurse, nurse's, nurses, nurses', nyers