```
declare @DT datetime
set @dt=getdate()
select dateadd(n, (datediff(n, 0,@dt)/5)*5,0),@dt
set @dt=dateadd(n,1,getdate())
select dateadd(n, (datediff(n, 0,@dt)/5)*5,0),@dt
set @dt=dateadd(n,4,getdate())
select dateadd(n, (datediff(n, 0,@dt)/5)*5,0),@dt
set @dt=dateadd(n,7,getdate())
select dateadd(n, (datediff(n, 0,@dt)/5)*5,0),@dt
```