Cardinals should be in groups of 6+ and corys in groups of 3+ so no it wouldn't be a good idea. A better alternative would be a male betta and 3 or 4 african dwarf frogs or if you want a group of fish a trio of cherry barbs and a couple of amano shrimp
Yes i agree with emma, a 5.5gal will simply not offer the space these fish need to thrive and shoal and perform other natural behavior. They can also be notoriously fragile, which is a problem in smaller tank set ups where water quality conditions can be more volatile.