2 significant digits.
Let's see what the range of possible values you can have for 1.3540980 if your uncertainty is +/- 2%
2% of 1.3540980 = 0.02 * 1.3540980 = 0.027082
So the lowest possible value for your result is
1.3540980 - 0.027082 = 1.327016
The largest possible result is
1.3540980 + 0.027082 = 1.38117996
Notice that only the 1st 2 digits of the result match which is reasonable since a 2% error means that your result is only accurate to within 1 part in 50.
