The Round template appears in the template list when a raster tile field, of type Tile, has been picked in the Transform pane. The template computes various rounding operations.
Round 
Rounding operations. Save the result into the specified Result destination using the specified numeric type. The Round to box allows choosing the decimal position for rounding, for example, rounding to decimal fractions like 0.001 or rounding to whole decimal positions like 10000.
Launch the template by choosing a Tile field and then doubleclicking the Round template. When the template launches we can specify options.

Round : down (floor) 
Take the source value of the tile in the given Channel and round down to the next lowest decimal position given in the Round to position value, and then save into the specified Result destination using the specified Channel type.
Using the default Round to position value of 1, a source value of 400.7 would round down to 400. 400.7 would round down to 401 (which is a smaller amount, and thus "down," from 400.7).

Round : to nearest (round) 
Take the source value of the tile in the given Channel and round up or down to the nearest Round to position value, and then save into the specified Result destination using the specified Channel type.
Using the default Round to position value of 1, a source value of 400.5 or greater fraction will get rounded up to 401 while fractional parts less than .5 will get rounded down to 400.

Round : to zero (trunc) 
Take the source value of the tile in the given Channel and round towards zero to the next highest decimal position given in the Round to position value, and then save into the specified Result destination using the specified Channel type. Equivalent to rounding down for positive numbers, and rounding up for negative numbers.
Using the default Round to position value of 1, a source value of 400.2 would round to zero to 401. 400.2 would round to zero to 400.

Round : up (ceil) 
Take the source value of the tile in the given Channel and round up to the next highest decimal position given in the Round to position value, and then save into the specified Result destination using the specified Channel type.
Using the default Round to position value of 1, a source value of 400.2 would round up to 401. 400.2 would round up to 400 (which is a larger amount, and thus "up," from 400.2). 
Everything Math  For a handy reference to anything in mathematics, see the Wolfram MathWorld site. Thank you, Wolfram!