Walmart is hit and miss as for anything being in stock. More miss than hit, actually. And, then I only find a few choices: Federal Champion, Winchester white box, and some oddball eastern bloc stuff (that I don't use). So, if I happen to be at walmart, I'll buy some range ammo, if they have it, and it's a decent price.
Buying online is much easier, offers a better selection, and is generally cheaper (in some cases MUCH cheaper). I can do it in my skivvies, sitting on the couch, while watching Jay Leno. Then, in a few days, the "big brown truck of happiness"
shows up at my office to drop it off. It just doesn't get much better than that!