Why do we round up 0.5000 to 1 instead of rounding down to 0?

Question

Why do we round up 0.5000 to 1 instead of rounding down to 0?

In: 12

Answer 1

.49999…., that is, .49 with 9 repeating forever, is exactly the same as 5. Infinity is weird.

.49999… rounds down.

5 rounds up.

We literally split five in half for this.

Granted, in practice, .49999…. is rare, while 5 is common. But it was as good of a reason as any for something that is completely arbitrary but had to be agreed upon in order for the community of mathematicians to work together.