Pricing by postal code

Hello There,

I have a pricing requirement that requires to charge Manhattan (New York - US) clients with a specific pricing. I maintained a condition record/access by postal code with the 5 digit zip code. However, i realized there are very large numbers 9-digit zip codes (which is the traditional 5 digit zip + 4 digits to add specificity) which are virtually un-maintainable, there are thousands of them and they are constantly being created. Is there a way to deal with this situation? How do I drive my pricing for Manhattan postal codes (New York) only?

Thank you