The problem is how you are comparing the Dimension values.
When you say
[Dim Trans Type Code].[Trans Type Code] ='10'
that is really comparing
[Dim Trans Type Code].[Trans Type Code].[All] to '10'.
You need to write your comparison like this:
IIF([Dim Trans Type Code].[Trans Type Code].currentmember IS [Dim Trans Type Code].[Trans Type Code].&[10],[Measures].CashDispensed,0)
That exampled is condensed but you can see the change for each dimension. This also requires that each dimension hierarchy is somewhere in your query. If not, then it's the All version of it and your IIF will not evaluate to the member you created.