RDF.XSD.Numeric.round

You're seeing just the function round, go back to RDF.XSD.Numeric module for more information.
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round(literal, precision \\ 0)

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Rounds a value to a specified number of decimal places, rounding upwards if two such values are equally near.

The function returns the nearest (that is, numerically closest) value to the given literal value that is a multiple of ten to the power of minus precision. If two such values are equally near (for example, if the fractional part in the literal value is exactly .5), the function returns the one that is closest to positive infinity.

If the given argument is not a numeric literal or a value which can be coerced into a numeric literal, nil is returned.

see http://www.w3.org/TR/xpath-functions/#func-round