Tax is there, not to raise money, but to move manpower from the private sector to the public sector - in other words to stop the private sector having the money available to issue job offers that bid people away from the public sector jobs we need doing.
If the robots are making people unemployed, then you don't need to tax any more in the first place. Just hire the people to work for the public good and pay them a living wage. They will then buy the output generated by the robots and the robot owners will save the money (because if they were spending the money then everybody would be employed sufficient to earn a living anyway). Increased turnover with existing tax percentages over a spending series then works its magic. Think a stone skipping across a pond.
Robots improve our standard of living. It's bad economics that insists everybody has to have a private sector job that is, perversely, incentivising the private sector to use labour rather than capital.
Ideally next to nobody should be working in the private sector. It should all be done by robots. We'd all then have a guaranteed job at a guaranteed living wage, yet we'd all have everything we want.
The Star Trek economy isn't as far out of reach as we think. It's 20th century economic thinking that is holding us back.