What is the difference between round half up and banker's rounding?

Round half up always sends a halfway value to the larger number (2.5 → 3). Banker's rounding (round half to even) sends it to the nearest even number (2.5 → 2, 3.5 → 4), which reduces cumulative bias over many values.

Can I round to the nearest 5, 10 or 100?

Yes. Choose "Nearest multiple" and enter the step — for example 10 rounds 47 to 50, and 0.25 rounds to the nearest quarter.

Is any data uploaded?

No — all rounding is done locally in your browser and nothing is sent to a server.

Rounding Calculator — Gera Tools

Rounding calculator

Round any number to a chosen precision and rounding rule. You can round to a number of decimal places or to the nearest multiple (5, 10, 100, 0.25, and so on), using one of several methods:

Round half up — the standard rule; halfway values go to the larger number.
Round half to even (banker’s rounding) — halfway values go to the nearest even number, which avoids the upward bias that accumulates with half-up over many figures.
Ceiling / floor — always round up or always round down.
Truncate — drop the extra digits toward zero.

All rounding runs entirely in your browser; nothing is uploaded.