QQ plot data regression

I'm reasonably new to Matlab. I have made a qqplot of 6 summed random dice rolls (6 dice rolled a number of times...lets say 100) and want to quantify it's approximation as a normal distribution (knowing that as the number of rolls increases it will approach a normal distribution).

To do this I created a qqplot to visualize it's like-ness (albeit with tails), and I know that if I can quantify the data's prediction of the regression line plotted in the qq plot I can determine it's fit, can anyone help me out with this step?