rounding error vs misreckoning

rounding error and misreckoning both are nouns.

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

As nouns, misreckoning is a hypernym of rounding error; that is, misreckoning 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
misreckoning: a mistake in calculating

Other hypernyms of rounding error include miscalculation, misestimation.

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