Is it still necessary to use bold and italic tags for seo?

[Happybranch980]

Does Google still look for bold and italic tags on a page for a higher seo score? I like to clean up as much code as I can so use them in my css style sheets but am I missing out on some optimisation as I use seo power suite and that keeps telling me i should be using <b> and <i> blocks on my page thus reducing my score as they are in my style sheets which powersuite cannot detect!