Face it you don’t have change, and who wants to stop at a toll booth anyways. You can pay for the tolls you blew through online at http://www.getipass.com/ within 7 days. Just remember which ones you went through (they are numbered), what direction, time of day, and the vehicle and plate info. It is better to just pay them online, and safer, not scrambling for change and stopping at the toll booth. Not to mention that is just isn’t convenient, especially in bad weather. Plus, some exits are iPass only, so there may not be any other option but to blow through. Note: I am not sure if you can be pulled over and ticketed for this, or what those consequences may be. If this is a concern, keep reading.
Now, if you are driving through Chicago often, or even not so often, I would highly recommend that you get an iPass at http://www.getipass.com/. I live down state and drive through Chicago maybe twice a year, but thought it was worth it. Of course, back when I got it I was actually stopping to pay tolls. It is $50, $10 for the transponder which is refundable and an initial $40 for your toll pool, which reloads automatically from your credit card at the $10 minimum pool. There is a bonus: the charge for tolls is half price with an iPass. In addition you won’t need to remember to do anything (within 7 days) and won’t have to go online to pay tolls every time you drive through. So after the first $25 in half-price tolls, it will have already paid for itself in dollars and convenience. If you have multiple vehicles, you can add them all to your account, to be used by the same transponder. If you don’t want to share the transponder or more likely think you will forget it in the other car, or if you want to carry one with you to use in rental cars, you can add a second iPass to your account for only $10 and pull from the common $40 toll pool. I mount mine to the windshield with 3M Dual Lock plastic strips (which are awesome and way better than Velcro for semi-permanently mounting moderately heavy, hard-backed devices) Two strips came with my iPass, but I needed extra strips to share between vehicles. For a temporary mount, like for a rental car, I recommend a suction style holder.