If you book through Airbnb, they do not take a security deposit until you need to pay for something you've damaged, soiled or broken. The host asks for a security deposit to protect their property from damage you might cause. If you leave everything as you found it, the security deposit will not be charged. There is only a refund if it was charged to your credit card before you arrived or if any damage costs less than the deposit. The tax is a tax imposed by cities for short term rentals, so that is not refunded. It is part of the total rental fee. What you see prior to booking is just the nightly rental fee, but you see the security deposit and tax when you book, so you know the full cost of booking.
