The same keyword has the same search volume for 6 ways to type it. How should I behave?

[gvnns]

the google keyword tool gives me those results:

5 x 1000             60500

5 per mille          49500

cinque per mille 49500

5 per 1000         49500

5per mille          49500

5permille           49500

The google results are different for every typing.

Let's say I decide to bet first on "5 per mille". should I neglect the other ways of typing, or shoul I use them all while writing the content and the metadescription of the page?

[AlanMosley]

if you use one, you will rank for all, but you will rank best for the one you include.
pick one and stick to it, dont go un-natural

[Nemek]

I'm afraid you might have fallen into the Google Adwords Keyword Tool "broad match" trap. Select "exact match" and then decide.

[petrakraft]

Seems to be a significant difference between 5 x 1000 and the rest. So if you want to rank with that term you should definitefely set up an extra page for that and treat that indivually. 5 x 1000 can mean everything ...

The lasting 5 terms are similar and we know that the search engines use synonymes, too - therefore we should definetifely use them. Althouth I made the experience that it is really difficult to rank with all synonyms. The best would be to set up a page for each term - what probably will be very difficult.