I simply avoid everything I can, and evade when it's smart to do so.
- find people growing food, and buy directly from them. there's a high chance it will be healthier, as they will have an actual conscience
- find independent businesses that sell other stuff for your home. try to get things from people outside your local gangster turf, it's harder for them to track the paper trail, so the people you buy from are more likely to use it as an opportunity to evade taxes themselves
- don't use the postal system for any of this, as the postal system is subsumed into your local gang's tax reporting
In most of these cases, it's not possible to stop people you trade with from paying some taxes, it's hard to be a business and avoid scrutiny of your finances. But the world's a big place, you can find businesses who trade outside of scrutinizers, if you just look for them