Basic4ppc uses the .Net Framework Round function.
Here is a quote from .Net documentation that explains this behavior:
Return Value
The whole number nearest a. If a is halfway between two whole numbers, one of which by definition is even and the other odd, then the even number is returned. Remarks
The behavior of this method follows IEEE Standard 754, section 4. This kind of rounding is sometimes called rounding to nearest, or banker's rounding.