I like to use thick lines with round join to get curved corners on lines.

Here is what it looks like:
http://cl.ly/1a42222U142I1K1B2y2M/content

But is there an easy way to get the following effect with rounded corners/join inside the line?
http://cl.ly/0a2g3O3u0t273i1S1K3U/content

I have to fake each inner rounded corner manually at the moment, and also have to redo them when I change the line.

Any help appreciated.

Thanks,
matt