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 $182.95   6.770%   $195.3357   $195.34   $195.35   $195.30  
  Purchase #2 $39.85   6.633%   $42.4933   $42.49   $42.50   $42.50  
  Purchase #3 $102.92   6.238%   $109.3401   $109.34   $109.35   $109.30  
  Purchase #4 $167.79   8.634%   $182.277   $182.28   $182.30   $182.30  
  Purchase #5 $53.66   3.795%   $55.6964   $55.70   $55.70   $55.70  
  Purchase #6 $116.75   13.673%   $132.7132   $132.71   $132.70   $132.70  
  Purchase #7 $141.38   4.179%   $147.2883   $147.29   $147.30   $147.30  
  7 purchase totals = $805.30       $865.1440   $865.15   $865.20   $865.10