Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $69.63   8.611%   $75.6258   $75.63   $75.65   $75.60  
  Purchase #2 $205.55   8.422%   $222.8614   $222.86   $222.85   $222.90  
  Purchase #3 $47.50   13.680%   $53.998   $54.00   $54.00   $54.00  
  Purchase #4 $51.85   11.567%   $57.8475   $57.85   $57.85   $57.80  
  Purchase #5 $242.77   8.242%   $262.7791   $262.78   $262.80   $262.80  
  Purchase #6 $82.26   6.267%   $87.4152   $87.42   $87.40   $87.40  
  Purchase #7 $182.77   4.184%   $190.4171   $190.42   $190.40   $190.40  
  7 purchase totals = $882.33       $950.9441   $950.96   $950.95   $950.90