Well, i would also charge above five dollars. Five dollars is something i would charge for something that took less than 30 mins to do. Be it doing dishes or drawing for someone.
UNLESS, I really liked the idea of the comission and it was sent digitally. Then i could charge a lot less. If someone wanted it in their mailbox it would be more expensive, since five dollars bareley covers shipping
You've got some skill, at least in this particular style.
Honestly, I think you should be selling these in the $10-20 range at least. Especially on your first example, there is plenty of detail that must have taken some time. Don't give that work away for a piddling $5.
DA is the worst place to try to sell art, since 1) most people here are artists and make their own so 2) only the very best artists get decent commission prices here because 3) there are people out there, of moderate-good skill level doing commissions for 10 points.
And FWIW 80points = $1 so your point price is higher than your cash price, not that it is necessarily a bad thing, points are only useful here on DA, so charging a premium for taking them is not a bad idea.
I would check and see if you can market elsewhere.
And my general rule of thumb is time it takes multiplied by amount you want to be paid, plus supplies. Remember things like time for advertising, electricity and computer programs ARE supplies, don't think you don't have supplies just because you are a digital artist. Also, IMO artist should be paid at least $10 per hour for their work.