polish vs round off

polish is a noun but round off is not a noun.

Word	Noun	Adjective	Verb	Adverb
polish	Yes	No	Yes	No
round off	No	No	Yes	No

As verbs, polish and round off are synonyms defined as:

polish and round off: bring to a highly developed, finished, or refined state

Other synonyms of polish include brush up, polish up, round.

polish (noun)	round off (noun)
the property of being smooth and shiny
a highly developed state of perfection; having a flawless or impeccable quality
a preparation used in polishing

polish (verb)	round off (verb)
bring to a highly developed, finished, or refined state	express as a round number
improve or perfect by pruning or polishing	make round
make (a surface) shine	bring to a highly developed, finished, or refined state