You can avoid a good bit of toll expense by taking I-88 and I-86 rather than I-90 across New York. In my opinion, it's a prettier route as well. It is a little longer distance (and time).
There are good reasons other than avoiding tolls to not take I-95 (or I-87) up via the George Washington Bridge; they are very much going through the middle of New York City, at least the Bronx, and so are busy, busy roads, sometimes slow, and often not all that smooth. You must also avoid nearly all of the parkways as trailers are restricted (and many/most also have some pretty low clearances). The Garden State Parkway is the notable exception; RVs are permitted on it throughout its length.