SQL Server 2008 :: Using Expression In GROUP BY Clause

I am working to move an application from MySQL to SQL Server. The person who developed the MySQL application has little database experience, and took some shortcuts that the lax nature of MySQL allows. One query with which I am struggling looks something like this:

SELECT StartTime + Offset, min(Sensor), max(Sensor)
FROM SensorData
WHERE SensorID = @SensorID AND
StartTime + Offset > @BeginTime AND
StartTime + Offset < @EndTime
GROUP BY (StartTime + Offset) / 100
ORDER BY StartTime + Offset

What we are trying to accomplish is to return minimum and maximum sensor values over a number of periods between the BeginTime and EndTime. When I run this query in MySQL on a sample dataset, it returns a small number of rows, with each one being the min/max values for a portion of the overall period.

Under MS SQL Server 2008, SP3, I get the two following error messages:
Column 'SensorData.StartTime' is invalid in the select list because it is not contained in either an aggregate function or the GROUP BY clause.
Column 'SensorData.Offset' is invalid in the select list because it is not contained in either an aggregate function or the GROUP BY clause.