Rounding semi-regularly confuses users who aim for star rating pass / FC
medals and then feel they have been cheated out of a medal because they
passed an "X-star beatmap", but the actual star rating of the beatmap is
slightly under X.
The latest instance of this can be found at
https://osu.ppy.sh/community/forums/topics/2091333?n=2. The relevant
beatmap there is https://osu.ppy.sh/beatmapsets/2162554#osu/4746232,
whose raw star rating is 6.9976070253117344.
The other direction would be to fix the star rating medals instead, but
I think this is more reasonable given we already do similar things to
accuracy displays.