1
general::
Also, in round figures. As an approximate estimate. For example, How much will the new highway cost, in round numbers? or In round figures a diamond of this quality is worth five thousand dollars, but it depends on the market at the time of selling. This idiom, which uses round in the sense of "whole" or "rounded off," is sometimes used very loosely, as Thomas Hardy did in Far from the Madding Crowd (1874): "Well, ma'am, in round numbers, she's run away with the soldiers." [Mid-1600s] Also see BALLPARK FIGURE.
American Heritage Idioms
2
general::
Phrase(s): *in round numbers [and] *in round figures
Fig. as an estimated number; a figure that has been rounded off. (*Typically: be ~; express something ~; write something ~.) • Please tell me in round numbers what it’ll cost. • I don’t need the exact amount. Just give it to me in round figures.
McGrawhill's American Idioms And Phrasal Verbs