You can curve grades in D2L by creating a formula grade item. Here’s the formula you’ll need to input:
( ( Original Score * 4 ) / 5 ) + X = Curved Score
For the Original Score, select the grade item for the assignment.
X is a number of points, and the amount X equals is determined by the highest grade achieved in the class.
Further information on this formula with a real explanation is available on the Division by Zero blog.