Anticipating this, I was looking into the history of the phrase "round number". It's a fairly old usage, predating the useful range of Google Books and Ngrams. I wasn't able to figure out whether rounding up and rounding down preceded, or came after round number. Also couldn't decide whether the term was in common use before mathematicians started writing down formal definitions such as "made up of a lot a small numbers as factors compared to it's neighboring numbers" which isn't what most of us think of as a round number.
@99,994 as I wrote this, so not much time to decide.