Interval Rounding

Hello,
  I have a table that contains a user's response and a timestamp at
which it was last updated.  I want to query for this response, and the
amount of time that has elapsed since, rounded to the nearest unit (e.g.
minutes, days, months, etc).  I am using:

SELECT NOW() - change_time
FROM ...

to get the interval, and am attempting to use either EXTRACT() or
DATE_PART() to get the appropriate value, but the interval doesn't
contain any unit higher than days.

Any thoughts on how I could accomplish this?  Thanks in advance

Mike Ginsburg
Collaborative Fusion, Inc.
mginsburg@collaborativefusion.com