Weed is legal in my state .. but that's not my kink. I fear jail. Tax evasion is whole 'nuther order of magnitude.
Exchanges now report 100% to the IRS how much was purchased.
All the Bitcoin I've ever sold has been at a loss or break even and I'll keep it that way because tracking costs is exceedingly complicated.
Hell , at this point I'll probably sell some Bitcoin just to load up my tax return with a little action. I know they know that I buy Bitcoin. Same way with my guns .. in my State .. they know EVERYTHING.