verizon lost the tethering case and they found it broke the fcc rules for the bandwidth that 4g uses to charge for tethering. i am rooted and use the built in of my rom. (a lot while traveling) but i have 2 friends with 7's and nexus who are not rooted, totally stock and use the built in tether on their nexus too. verizon was forced to take down the redirect to their Site that used to force you to pay an extra 20$ for the data you already pay 30$ for.
so just use the stock tether function, if it doesn't redirect you to a Site that requires you to sign up and pay. then it's part of whatever data plan you have. They both said they researched it after the jelly bean update broke foxfi tether app, and found out the redirect had been pulled because of the court case verizon lost.
oh and if you don't need the extra speed of WiFi tether, bluetooth tether works great and doesn't eat battery like the WiFi will. since my phone screen is off and it's the biggest battery drainer, when I bluetooth tether my phone battery still seems to last just as long as if I was using the phone instead of the tab. where WiFi will burn thru a battery in no time.
Good luck. and if you want, there's a text app for your tab that I use that allows you to send and receive them from the tab without picking up the phone. So I leave the phone in my back pack and do everything from the tab while I had it put. no switching back in forth.