I too registered on Care.com not too long ago, and was very dismayed at the pay rates I saw. That's the reason why I didn't heavily pursue any listings in my area. I can understand getting paid five bucks an hour for the occasional casual babysitting job of one child, but even the website itself has a disclaimer stating that all potential employers on there are subject to minimum wage laws, with said casual/occasional care gigs being the only exception. There was no way I was willing to watch multiple children as well as shuttle them around in my car for five dollars an hour - no way, no how.
Many people (at least in my area, but apparently in other places as well based on the comments in this thread) are lowballing on there. I would think that when finding someone to care for your children, that isn't something someone would want to skimp on!
I would expect at least $10.00 an hour, plus mileage if they're wanting me to do pick-ups, drop-offs, etc. Of course I'd be willing to negotiate, but five dollars is just way too little.