As a rough estimate the area of the ellipse that results from a round drill bit entering at an angle with be a factor of times larger than if the drill bit was perfectly perpendicular. So for the values you asked about the amount of excess area is:

1 degree: 0.02%

2 degrees: 0.06%

3 degrees: 0.14%

4 degrees: 0.24%

5 degrees: 0.38%

This assumes that the error is in alignment in one axis only so the resulting hole is an ellipse. If the drill bit is allowed to "wander" in a curcular manner to create a larger diameter round hole then the areas would be larger - up to 0.77% for the 5 degree misalignment.