rounding error vs misestimation

rounding error and misestimation both are nouns.

Word	Noun	Adjective	Verb	Adverb
rounding error	Yes	No	No	No
misestimation	Yes	No	No	No

As nouns, misestimation is a hypernym of rounding error; that is, misestimation is a word with a broader meaning than rounding error:

rounding error: (mathematics) a miscalculation that results from rounding off numbers to a convenient number of decimals
misestimation: a mistake in calculating

Other hypernyms of rounding error include miscalculation, misreckoning.

rounding error (noun)	misestimation (noun)
(mathematics) a miscalculation that results from rounding off numbers to a convenient number of decimals	a mistake in calculating