Sales taxes cause burdens on local exchange, while tariffs cause burdens on international exchange. In both cases, you're losing wealth in the name of maintaining a state. In the case of tariffs, you're incentivizing local production, which feeds independence, while in the case of sales taxes, you're incentivizing international production, which feeds interdependence.

Actual rates are less interesting to me than matters of incentives. If pressure is to be imposed on the economy, I want it to be pressure to maintain small local production, and keep governments from getting to be too friendly with one another.