Template:Rnd/doc

Usage
This template rounds to  decimal places (goes the other way for negatives) and includes trailing zeros. Scientific notation is used for numbers greater than or equal to 1, or less than 1.

Compare: As with #expr, the total number of significant digits is not more than 14:
 * gives 2.0004
 * whereas gives
 * gives 0.000020004
 * gives 0
 * gives 154268
 * whereas, even though  (see m:Help:Format produced by expr)
 * whereas, even though  (see m:Help:Format produced by expr)

Internal details
The template calls Template:Rnd/b1 if the number, after rounding, is positive, Template:Rnd/b-1 if it is negative, and Template:Rnd/b0 if it is zero.

Their first parameter is the rounded number, their second the rounding parameter, and their third the value of the condition that the rounding parameter is positive.