This has nothing to do with rounding. A balance due of $1025.28 is more than the safe-harbor amount $500. Presumably you did not meet one of the other safe harbors, so an underpayment penalty of something like $65.19 is to be expected.
http://taxes.marylandtaxes.com/Individual_Taxes/Individual_Tax_Types/Income_Tax/Payment_Information/...
Normally TurboTax calculates and includes in your balance due the expected underpayment penalty, but you have the option to tell TurboTax to omit the penalty and let Maryland calculate and bill for the penalty.
