How to pronounce “round number” in English

It's a good round number, you know?

That's a bit close to a round number.

But I completely rounded it to a sort of punchy round number.

Good, round number.

Other than just picking a nice, round number, what evidence do you have the four to six is really what's necessary?

For instance, even when I started today, and a lot of times when I start on stage, I start at $1,000, because it's a nice round number.