適当にいくつかの表現を集めてみた
wikipedia(en)とかを参照

切り上げ=round up/round away from zero
切り捨て=round down/truncate/round towards zero
天井関数=ceiling/round towards positive infinity
床関数=floor/round towards negative infinity

その他に、
round half up
round half down
round to even/round half even