I know there is no use to nofollow links that leads to other internal pages, but my banners appears on every page of my site, and they're both linking to two articles in the same site. Should I nofollow them?
In addition to comments from John:
Nofollow is a value that can be assigned to the rel attribute of an HTML a element to instruct some search engines that the hyperlink should not influence the ranking of the link's target in the search engine's index.
It's Sounds Like the Banner is for a sales page and it requires link juice to perform higher in serp's (If you want to rank your landing page in google) Nofollow is good for some out bound links but, for every internal link it must be a dofollow link so that the link juice should follow from page to page.
"No follow" is rather used to mark external links. In your case you don't have to assign them anything.