Rental car toll payment

I am wondering if it's possible for me to pay tolls online before the rental car company gets billed and ends up billing me. I'm assuming they will tack on a bunch of extra charges.

My rental car had out of state plates and no toll tag, so I went through the far right lane assuming that I could pay cash, but it looked like the toll booth was closed and people were just driving right through at low speeds.

I tried putting in the rental car license plate online but nothing came up, then I saw in the notes at the bottom that rental car drivers should contact the company to make payment.

Any ideas?