round() increases or decreases (PR#9195)

G'day Gael,

"GM" == gael millot <gael.millot at curie.fr> writes:

GM> I have a strange behavior with round() when it has to deal
    GM> with 5. [...]  It also happens with signif()

    GM> Is it normal ?
The "Details" section in the help page of round (?round or
help(round)) suggests yes.

Cheers,

        Berwin