Loss of data SSIS Data Transformation

Hi,

 I am using SSIS to transform the data from Excel Source and put it in SQL.  Data transfrmation.  I have defined Column InterestRate as Decimal(9,6) in Database. In SSIS i am taking this column from Excel Source as String and Casting it to (DT_DECIMAL,6) in the derived column.  If the data is 5.6 in excel, in DB i get 5.600000. If the data is 6.77, in the database i get 6.769999 ( randomly i get this type of data ).   I just wanted to find how to avoid such data discrepancy while doing data  transformation. i put data viewers in between shapes in the package and the data seems to be good. But i dont understand how the data is transformed rom 6.77 to 6.769999 when it goes in to the DB.

Thanks,

-Prasad  

-Prasad