They restrict individual strand movement within the bundle, and therefore are not recommended. The picture below is an example of a finished cable using tie wraps to secure the wire bundle. IDE cable, single wire per strand, bundled with tie wraps. Click on image to see blowup view. Another way to secure the strands is to bundle them inside a flexible plastic wire conduit.
Flexible conduit is affordable and available in most hardware and electronics stores.
It's slightly more work than using the tie wrap method, but is not difficult to work with. Some argue that it's the most cosmetically appealing method. Wide SCSI cable, single wire per strand, bundled with conduit. Click on image to see blowup view. By now you have a pretty good idea of what it takes to round your ribbon cables and some of the benefits.