ROUND « Date Timestamp Functions « Oracle PL/SQL Tutorial

13.15.1.The ROUND Function
13.15.2.Datetime Formatting Parameters for ROUND(x[, unit])
13.15.3.ROUND(x[, unit]) : round x. By default, x is rounded to the beginning of the nearest day
13.15.4.Round date to day
13.15.5.Rounds May 25, 2005, to the first day in the nearest month
13.15.6.Rounding to the Nearest Minute
13.15.8.Round result from months_between