Use Linq To Split Data Up Into Several Reports

I have a query where I grab data from a stored procedure and then use linq to split the data up into several reports.The problem I am having is that all of my columns that are decimal(18,2) in the database are getting rounding somehow by the end. From debugging it definately looks like the Linq query is what is rounding the value.

The reason for the datatable is that I need to pass the data to a function that creates an excel file this function needs a datatable so it can determine what the data type of each column is. Linq doesn't seem to preserve the type.

Code:
Dim err = From p In DetailData.Tables(0).AsEnumerable()
Dim dt As New DataTable
dt.Columns.Add("kWh", GetType(Double))
Dim tu = From p In err _
Where p(countType) > 0 _
Group By Key = p.Field(Of Int32)("Group") Into Group _

[code]...