I've been using 205/60 X 16 tires on my SVT for the past 2 years! I have had no issues, rubbing, etc. They are about 5% bigger then stock size and your odometer will be off by that amount. Really about 4.5%. You will record fewer miles then you are actually traveling so you would have to adjust your MPG to get an accurate number. My speedometer is still accurate however. Not sure why that is but when I pass radar speed signs the speed posted showing how fast I'm going is usually right on or off by just 1 mph.
Using the tacomaworld.com tire calculator (see previous post), this clearly supports your findings. Your speedo has mfg tolerances, hence your observation as to speed:
205/55-16 205/60-16 Difference
Diameter inches (mm) 24.88 (631.9) 25.69 (652.4) 0.81 (20.5) 3.2%
Width inches (mm) 8.07 (205) 8.07 (205) 0 (0) 0%
Circum. inches (mm) 78.16 (1985.17) 80.69 (2049.58) 2.54 (64.4) 3.2%
Sidewall Height inches (mm) 4.44 (112.75) 4.84 (123) 0.4 (10.25) 9.1%
Revolutions per mile (km) 810.68 (503.73) 785.21 (487.91) -25.47 (-15.83) -3.1%
example reading between the two sizes at 55mph -
speedo reading actual speed
55 mph (88.51 km/h) 56.78 mph (91.39 km/h)
remember that each tire mfg has slight deviations in the above #'s (dia., width, circum., sidewall hgt.) These #'s listed are not etched in stone.