No Tolls on I-95 south of Washington DC. We always take I-95 to I-4. I think its the fastest.
As one poster said you may want to avoid major cities during rush hour. In particular, DC and Richmond. Although the bypass around Richmond usually takes care of any traffic issues, and doesn't add that much time.
But from Richmond to Jacksonville, you shouldn't have too much traffic. A little slot of congestion around Fayetteville NC normally, but all in all its a good trip, and one that I thought I'd dread three years ago, when I first made it. But one that I now look forward to each year. The benefits of having a car in Disney make it well worthwhile for me.
However, do avoid DC at rush hour. There is nothing worse than a long trip, starting with bumper to bumper traffic on the beltway around DC. We are considering taking I-81 down into the Carolinas this year, and skipping across to 95, because it looks like we may have to depart at a time where we'd be stuck in Friday night rush hour DC traffic. But we don't leave til December, so that might change.