Here's the update:
They get you coming and going! Interstingly, the tax rates are pegged to old values, with P1s going for 50isk/unit and P2s going for 900isk/unit, and P3s for 7000isk/unit. This results in interesting tax rate anomolies as shown above. There are a few errors, as I lumped a few things together in the beginning and I can't sort the out now. Stupid March 11. But the overall tax rate of 18% is correct. If I had no taxes, I'd be at about 51m in profit 11 days in.
Edit: My original effective tax chart was poorly formatted. I updated it.