You won't find hardly any real dogs worth tending with in the USA. Most of the tending breeds have been turned into the police dog/ man biters here. The german shepherd dog, old german shepherd dog, any of the belgian shepherds including the malinois, lakenois, and turveren and France's beauceron. There are video links in my above post if you would like to see them work. Ulf has GSD's and Gearry Loff has beaucerons.
Extensive, expensive expert breeding and training are necessary to turn out useful dogs, whether tending or herding. I can hold animals on an unfenced graze with border collies or kelpies just as well, but by placing the dogs where I want rather than having them patrol a graze with boundaries. And of course, they learn they are just "holding" the animals in a set place, and not gathering them to take them somewhere else. Napping on your feet while leaning on your staff becomes a great skill to learn.
You
should go to www.whitecloversheepfarm.com and read some of Ulf's articles or view his videos on youtube. Leerburg has a few tapes on tending training and the HGH tending trials in Germany available.
Once again, it's not the breed, but a specific line within a breed selectively bred to tend, and then appropriately trained in that manner. An expensive pre-trained dog is the cheapest herding dog there is in the long run.