浮点数不是精确值，所以使用它们会导致舍入误差。

Floating point Numbers are not exact, and manipulating them will result in rounding errors.

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将双 精度浮 点值按指定的小数位数舍入。

Rounds a double - precision floating - point value to the specified number of fractional digits.

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如何舍入到最近的十进制值的浮动值？

How to round off the float value to nearest decimal value?

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