You can cancel without penalties if the booking was an Instant Booking. There is a link within the cancellation help pages which outlines the procedure. There is a level of "attest" to these cancellations, but if you haven't used your quota, they're there for use.
If you do want to book with the least penalties then make sure that you use a desktop. A mobile device is more punitive as it doesn't allow lesser punitive options a desktop will. For instance, on a desktop you can cancel and block dates, or leave them open. On a mobile device you don't get those options.
Even where Airbnb state "No Charge" cancellations, there are penalties, so just be aware when going through the process.