There are initially \( 2^8 \) = 256 possible tiles. Most of these will be rotations of each other, but some will have less rotationally symmetric partners.
There are 4 tiles which have 90 degree symmetry and thus no partners;
and there are 6 tiles which have 180 degree symmetry, and thus come in twos. (See image)

The rest will come in fours.

Split the 256 tiles along these symmetries:
4 + 12 + 240
And divide each total by its number of partners:
4 + 6 + 60
For a total of 70 distinct tiles.

(These tiles form the basis for the solitaire tile game Izzi.)