You should use nofollow only for linking sites you don't trust or endorse, sponsored links, etc. but not for internal linking, the PageRank sculpting days of this method are long gone, and you'll just burn your link juice and impair it's flow throughout your site.
If you need to exclude some pages of your site from being indexed just use the noindex meta tag.
Check the following resources:
Should internal links use rel="nofollow"?