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 $107.59   8.754%   $117.0084   $117.01   $117.00   $117.00  
  Purchase #2 $99.28   10.510%   $109.7143   $109.71   $109.70   $109.70  
  Purchase #3 $65.95   3.630%   $68.344   $68.34   $68.35   $68.30  
  Purchase #4 $180.89   13.838%   $205.9216   $205.92   $205.90   $205.90  
  Purchase #5 $133.26   5.675%   $140.8225   $140.82   $140.80   $140.80  
  Purchase #6 $33.95   13.874%   $38.6602   $38.66   $38.65   $38.70  
  Purchase #7 $46.70   11.248%   $51.9528   $51.95   $51.95   $52.00  
  7 purchase totals = $667.62       $732.4238   $732.41   $732.35   $732.40