Hi Gina,
I'm in Manatee County as well. There's no easy way to do this. I have adjusted my nightly rate and cleaning fee to include the 5%. I state in my listing that rates include the Manatee Cty occupancy tax. I think you could also create a fee with a 5% rate that would add to the nightly rate. I had an email conversation with cust service and they were not helpful. AirBnb wants you to either send a separate $ request after you get a booking or collect from the renter after they show up. I don't think either are good or practical. I think renters want to know all the charges when they book. My solution is less than ideal but works better for me than what AirBnb has suggested.