<< ...for the case of a box you can turn on control points with Edit> Show pts and modify them like Marco has shown. >>

My first intuition was to try and grab the points and move them (as in the example given), but for some reason it didn't work for me. I must have been doing something slightly different.

<< So for example in the case of a tapered box, you could draw one rectangle at the base, and then a 5x5 rectangle at the top and then use the Construct> Loft command to build the tapered box directly that way. >>

That is exactly how I created the example in the original post, but I was wondering if there was another way to do it. I am still a beginner with NURBs and have a lot to learn.

Thanks to everyone for their help.