taxes in items sold

Hi,
I am using ecart from the supersuite for dreamweaver cs3. My client's business is out of NY. I have to set up the cart so that all ny residents are charged the ny state tax as well as their county taxes. Also all items sold and their shipping costs have to be taxed. I know that I will have to list all of the counties in ny and the tax. How do I set up the cart so that if a customer selects ny as their state they have to pick their county? And those outside of Ny state are not required to do this? How do I set up the cart so that taxes for ny residents are charged on the item and shipping? where as those outside of ny state are not?
Thank you,
K