DoubleExtensions

Rounds using arithmetic (5 rounds up) symmetrical (up is away from zero) rounding

d

A double number to be rounded.

decimals

The number of significant fractional digits (precision) in the return value.

mode

The midpoint rounding mode

Возвращает: The number nearest d with precision equal to decimals. If d is halfway between two numbers, then the nearest whole number away from zero is returned.