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 $117.40   7.247%   $125.908   $125.91   $125.90   $125.90  
  Purchase #2 $45.38   11.845%   $50.7553   $50.76   $50.75   $50.80  
  Purchase #3 $152.29   9.727%   $167.1032   $167.10   $167.10   $167.10  
  Purchase #4 $127.66   9.516%   $139.8081   $139.81   $139.80   $139.80  
  Purchase #5 $59.61   3.587%   $61.7482   $61.75   $61.75   $61.70  
  Purchase #6 $174.98   11.616%   $195.3057   $195.31   $195.30   $195.30  
  Purchase #7 $201.27   4.165%   $209.6529   $209.65   $209.65   $209.70  
  7 purchase totals = $878.59       $950.2814   $950.29   $950.25   $950.30