rounding decimal points in an expression

This sounds so simple but yet don't know why it doesn't work.

i've got two decimal numbers in columns

closingUnits = 25093.53640

closingAmt = 59110.33

i use a derived column transformation to generate a string column which is the division of those two above.

mystrfield = closingAmt /closingUnits = 2.355599

what i want is cast it to just 4 decimal points when i run the expression below it cast it to 4 decimal points but it doesn't do any rounding.

the value i get is 2.3555 when i should get 2.3556

(ISNULL(closingAmt ) || closingUnits == 0) ? "0.0000" : ((closingAmt / closingUnits) < 1 && (closingAmt / closingUnits) > -1 ? "0" : "") + (DT_WSTR,15)(DT_DECIMAL,4)(closingAmt / closingUnits)

Found the answer,

silly me, it's ROUND duh!!!

http://msdn2.microsoft.com/en-us/library/ms141721.aspx