Niceness rhymes with:
callousness, carelessness, cautiousness, consciousness, contagiousness, contentiousness, dangerousness, disingenuousness, fractiousness, graciousness, hellaciousness, helplessness, hoarseness, homelessness, hopelessness, joblessness, lawlessness, lessness, nervousness, outrageousness, pompousness, powerlessness, rebelliousness, recklessness, restlessness, righteousness, ruthlessness, seriousness, surfaceness, terseness, weightlessness
Niceness sounds like:
nagging, nakanishi, nakasone's, nanchang, nanjing, nanking, nasons, new-mexicans, nickens, nicknames, nissan's, nissans, nixon's, nixons, niznik, non-nonsense, noneconomic, nonsense, nosiness, nosing, nuisance, nuisances, nunsense