This has nothing to do with whether or not you pay tax. You pay tax on income even if it is not related to digital currencies.

If you somehow made $100k off V-Bucks then you need to report that income, but you should say "No" to the question about digital currencies.

(Disclaimer: I can't believe I have to say this, but if you are making significant money off of video game currencies you should talk to a professional rather than listening to an anonymous HN poster as your sole tax advice)