I'm going to be registering six .com domain names for some CPA programs
and would like to do it in bulk to save some money & time.

Where's the best place to register them with some coupon codes
that also includes whois privacy.

The last time I purchased bulk .info (more than 6) domains from godaddy I got free whois privacy. So I'd suggest you take a try there just to see how much it comes to the final value, then decide on other registrars.

I am not sure if Godaddy 1 dollar .com offer is still available, but you can check Godaddy.com, Namecheap.com and Name.com. They are all good registrars (godaddy??) and the last two offer free whois privacy for free.