Okay, so after doing research, I apparently don't have the "Honda Insight" Potenza RE92 tires that everyone raves about. But I did just go outside today and check my tire pressure (was at 30 psi).
So the recommended pressure on the plate inside my door jam says 32 psi, and the max sidewall pressure on my tires says 44. I inflated them all to 40 psi. I'll let you know if that boosts my mpg at all, though I am in the middle of a tank, so the mileage numbers will be lower than if I changed the pressure at the start of a fresh tank.