Tightenings rhymes with:
fastenings, happenings, openings, poisonings, questionings, seasonings, bannings, beginnings, browning's, burnings, canings, corning's, drownings, earnings, earnings', evening's, evenings, fanning's, fastenings, happenings, hennings, innings, jennings, leanings, lightnings, linings, manning's, meanings, mining's, morning's, mornings, openings, pennings, poisonings, questionings, runnings, screenings, seasonings, signings, underpinnings, vining's, warnings, winings, winnings, yearnings
Tightenings sounds like:
tajikistan's, tastiness, tasting, tastings, techsystems, tectonic, tectonics, testimonies, testing, thaxton's, ticketing, tightening, tightens, tightness, toasting, touchdowns, twisting