I learned a cool age-related compound yesterday. One of my roommates asked me how old I was, and when I answered she said, "Ah, you 四捨五入 to 30." I had to get her to write out the kanji before I could wrap my head around the pronunciation, and then show some actual examples with numbers before I understood the concept. My age rounds up to 30. (Not that this is a new phenomenon; I’ve rounded to thirty for a whole year, now, but I think it was the first time she realized it. It makes us 仲間 somehow, since she rounds down to 30.) 四捨五入 (ししゃごにゅう) seems like a long, complex way to say rounding, but that’s how they do it here, so get used to it.
Discard four, enter five.
If I stretch my mind a bit I can kinda see the sense in that, but it’s certainly kinda… yeah.