round time to minutes

Hi all, 
I have a Global.asax page checking for auction end times every 60 seconds. 
Where au.endDate = DateTime.Now.ToString() _
 
However Date time is stored to seconds in the database, so i need to round "enddate" and "Datetime.now.ToString" to minutes so i only need to run the task once a minute and it will pick up the endDate??
Regards

 
...