Your tank isn't doing anything that all of the other "plug-n-play" tanks don't do...they ALL run right around 80*F, give or take a degree or two.
Does your model have an "open sump" area (meaning the lid doesn't cover it)?
If the sump is "open", you can get a small fan made for this purpose (JBJ makes one called the C-breeze). That will give you a couple of degrees or so.
Does it have a hinged top or a glass lid?
If the top is hinged, leave it "ajar" (prop is slightly open), and/or leave the feeding door open to vent the hot air out.
If you have a glass lid, remove it and use egg crate instead. I don't recommend going "open-top" as ANY fish can, and will jump...even sluggish bottom dwellers and lionfish.
Which lighting are you using?
Use a low-heat lighting technology. Also, only run your lights when you're home to see the tank...don't run them all day "just because", but run them in the evening when you're home and it's cooler.
One thing you can do is swap out the stock pump for one that is cooler-running (draws fewer Watts). I've REALLY been liking the Sicce Syncra Silent pumps for this modification. They're low-power draw and are super quiet...more quiet than any of the small pumps I've used to re-pump PnP setups (we have several that we use for QT's and growout tanks for small specimens).
Add an airline to increase surface agitation...this will help bring cooler air into the water, and will aid in evaporative cooling.
Oh, and the more pumps you use (powerheads), the more your water will heat up, so be sure to use low-draw powerheads if you must use them. Unless you're running a reef (you didn't say), you really don't need them at all in a tank that small, IME/IMHO.
Those are about the best things you can do without running a chiller.