ROUND is very similar to the TRUNC function.
It uses the same format mask as TRUNC.
ROUND rounds up or down based upon the format mask.
The default mask when specifying a DATE value is DD.
Some useful purposes for this are
Rounding to the nearest minute for billing cellular-based calls
Rounding to closest month to determine a pay period
The Syntax for the ROUND Function
ROUND(input_date and time or number,rounding_specification)