Seventieth rhymes with:
montieth, ninetieth, eightieth, fiftieth, fortieth, montieth, ninetieth, sixtieth, autenrieth, eightieth, fiftieth, fortieth, montieth, ninetieth, sixtieth
Seventieth sounds like:
savant, seventh, seventy, shipmate, shipment, siphoned, spanned, spawned, spend, spent, submit, submitted, subpoenaed, suspend, suspended