.45*215*2 = 193,5 mm of tyre height. Diameter of the wheel is 62,53 cm. .45*225*2 = 202,5 mm of tyre height. Diameter of the wheel is 63,43 cm. This means that a wheel with 225/45 is 9 mm higher or 0,35433 inch. If your Prius is not lower than stock, it will probably fit. You will have a 1,5% slower speed indication, which will still be higher than your actual speed. (Mine reads 107 kph when Tomtom says 100 kph.)
The OEM 215/45-17 is actually smaller in diameter than the OEM 195/65-15. The 225/45-17 diameter is a perfect match in diameter to the 195/65. Why did Toyota go with the 215/45? Not as wide as the 225.