Toughen rhymes with:
mcguffin, mcmuffin, muffin, acetaminophen, altenhofen, carstarphen, dalfen, deafen, dextrathoraphan, dolphin, draffen, entoffen, farfen, geffen, giffen, griffen, griffon, hafen, hanifen, hyphen, ibuprofen, kniffen, lafon, ludwigshafen, mcguffin, mcmuffin, morphin, muffin, offen, often, orphan, paraffin, siphon, sniffen, soften, steffan, steffen, stephan, stiffen, sutphen, syphon, tamoxifen, xenophon
Toughen sounds like:
tacoma, tajima, takashima, takashimaya, takayama, taken, takeshima, takin', taoism, tashin, tashjian, tasm, tasman, tasmania, tasmanian, tassin, tassone, tatsuno, tauzin, teason, techno, tecogen, teichman, teichmann, teigen, tejan, tejano, tejon, tessman, texan, texscan, tezeno, theisen, theism, theissen, thicken, thiesen, thiessen, thissen, thyssen, tieken, tieszen, tietjen, tigon, tijuana, tishman, tison, tognino, token, tokkin, tokuyama, toscanini, toscano, towson, toxin, tschumi, tsunami, tsuneo, tuchman, tuckman, tucson, tucuman, tudjman, tugman, tuscan, tuscany, twosome, tycoon, tyson