Grouping records based on intervals of time
select dateadd(minute, 1+datediff(minute, 0, CaptureTime), 0),
       sum(SnapShotValue)
from YourTable
group by dateadd(minute, 1+datediff(minute, 0, CaptureTime), 0)


SE-Data

datediff(minute, 0, CaptureTime) gives you the number of minutes since 1900-01-01T00:00:00.   

dateadd(minute, 1+datediff(minute, 0, CaptureTime), 0) adds the number of minutes since 1900-01-01T00:00:00 to 1900-01-01T00:00:00 ending up with a datetime with only minutes. 

The 1+ is there because you wanted the next minute.

To do the same with a 5 minute interval you need to do some calculations. Divide the minutes with 5 and multiply with 5 gives you the minutes rounded down to a 5 minute precision. This works because the result of an integer division in SQL Server is an integer.

dateadd(minute, 5 + (datediff(minute, 0, CaptureTime) / 5) * 5, 0)