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 $242.38   8.204%   $262.2649   $262.26   $262.25   $262.30  
  Purchase #2 $249.80   6.334%   $265.6223   $265.62   $265.60   $265.60  
  Purchase #3 $151.26   4.238%   $157.6704   $157.67   $157.65   $157.70  
  Purchase #4 $209.69   11.409%   $233.6135   $233.61   $233.60   $233.60  
  Purchase #5 $212.58   6.141%   $225.6345   $225.63   $225.65   $225.60  
  Purchase #6 $230.81   12.865%   $260.5037   $260.50   $260.50   $260.50  
  Purchase #7 $58.81   12.303%   $66.0454   $66.05   $66.05   $66.00  
  7 purchase totals = $1,355.33       $1,471.3547   $1,471.34   $1,471.30   $1,471.30