If you search this forum for "keyword density" you will find that opinion is divided whether search engines look at such a thing. I don't think they do (at least not as a constant) but others think they do.
The exact percentage of keyword density tolerance of major search engines is still not known. The algorithms of the top search engines differ as well as the opinons of experts are different on this.
Repeat the most important keywords one time in the keyword tag, show it at the start point. Try to repeat the keywords in description and show it in the domain.
It has very little value (indeed no value) .. go with quality inbound links it will free you from all other outdated worries.