I think he doesn't want tax with Bitcoin at all. Initially he created it to help us solve a lot of taxes from government and local agencies out of our assets and our finances. However, tax is an indispensable thing for every country to operate stably and well. As for bItcoin, fees from transactions can be viewed as tax, which helps both the system and transactions work stably and smoothly.
If you check whatever communication made by Satoshi during 2009-10, it is clear that he intended Bitcoin to act as a currency, and not as an investment asset. He hoped that in future Bitcoin will be accepted as a global currency and used by billions of people. But he probably didn't predicted that Bitcoin will be used more as an investment asset, and less as a currency. Now this complicates the whole thing. Currencies are not subjected to capital gains tax. If you do forex trading, a different type of tax is applied. So my guess is that Satoshi never thought about the taxation part, since he never thought that Bitcoin will become an investment asset.