I would think that 5 cories is a bit much in a 10 gallon, I'd say 4 and a Betta would Pretty much fill it out. I'm sure you can do it though, but I have a "formula" that I try to stick to to make sure I'm understocked!
Basically my formula is to "square" (as in "Pie-R-Squared") the length of any fish and try to stick to that in gallons. For instance let's take a fish that gets to be 6". Many would err to the inch per gallon rule and say that you can house one of these or six 1" guppys. There is obviously a difference (as has been regularly petitioned against on this site!

) But if you square six, then you come up with 6x6=36.....meaning a 6" fish should have a 36 gallon aquarium (or larger) to live in. This isn't a rigid rule, but rather a framework to work around, and as the aquarium gets larger, I tend to allow other fish to be allowed as well. This rule, more than anything is for the fish to have room enough to move around a bit. An example is my custom made Display aquarium. It is 5'x22.5"x2' (basically 150 gallons) which actually holds about 125 gallons of water, and I house my Blackbelt Cichlid in it. This fish will get to about 1 foot in length (only 9" now). I also "allowed" a Sailfin Pleco in the tank (which is moderately planted, and will become heavily planted), which can reach up to 20 inches length. To be honest, the only reason I added any other fish than the blackbelt was for algae cleanup (and for minor interaction for the fish....Plecos are nocturnal). Anyways, the tank is built as a 150 gallon which supports my "formula" of 12" of fish x 12= 144 gallons. In all actuality, this tank is nowhere near the area this fish needs to live in nature, but I think it will be able to thrive in this tank for the duration of it's life! It is a new setup with moderate to few plants and I never let the nitrates get above 20ppm. Eventually (especially after I add my canopy and extra lights), there will be many plants to take up any pollutants and provide cover for my fish. This setup works well because the Blackbelt is active during day, while the Pleco at night. Also, my 55 gallon houses 8 Florida Flag Fish (averaging maybe 2" topps) and four 1/2" dwarf puffers. I consider this tank fully stocked, already. If I get any more fry out of my FFF, I'll move them to one of my smaller tanks. For argument's sake, I consider the full sise of the fish and 2" average FFF squared is 4" x8 (how many) is 32 gallons. Now the Dwarf Puffers are not fully grown either, and will become 1", but are considered messy fish, so let's double their size (which will square to 4", again) I have four of these fish, so 4" x 4 is 16 gallons. 16 + 32 + 48 gallons, but I also know that male FFF can get to around 3" fully grown, so this tank is fully stocked and very active, anyways! Sorry about lots of info, but just trying to describe my method of stocking.
I will say that a 10 gallon is relatively large in bottom area compared to other common aquariums. It's 20"x10" surface is nice in comparison to a 20 gallons 24"x12" surface. You can almost hold the same amount of bottom dwellers (area-wise) but have half the gallons to deal with waste-production.