Using 8*8 and then using 0.5 tiles around each sides, we would be able to achieve
as described in the attached image (1) , which is similar to Mridula's reply...


till this step we would be able to use 80 tiles, but it would not come to a perfect square

If the tiles are identical from all the 4 corners also, then if we move the any of the 2 opposide sides comprising of all 0.5 tiles we would be able to fit 1 more tile (0.5 on top and 0.5 at bottom) as in the attached image (2)


We would still have 1 tile left