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 $83.38   13.528%   $94.6596   $94.66   $94.65   $94.70  
  Purchase #2 $206.74   8.830%   $224.9951   $225.00   $225.00   $225.00  
  Purchase #3 $46.60   8.360%   $50.4958   $50.50   $50.50   $50.50  
  Purchase #4 $123.99   12.827%   $139.8942   $139.89   $139.90   $139.90  
  Purchase #5 $24.36   4.378%   $25.4265   $25.43   $25.45   $25.40  
  Purchase #6 $90.50   9.863%   $99.426   $99.43   $99.45   $99.40  
  Purchase #7 $177.92   10.765%   $197.0731   $197.07   $197.05   $197.10  
  7 purchase totals = $753.49       $831.9703   $831.98   $832.00   $832.00