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 $85.25   10.210%   $93.954   $93.95   $93.95   $94.00  
  Purchase #2 $132.64   11.642%   $148.0819   $148.08   $148.10   $148.10  
  Purchase #3 $182.71   3.814%   $189.6786   $189.68   $189.70   $189.70  
  Purchase #4 $120.77   12.275%   $135.5945   $135.59   $135.60   $135.60  
  Purchase #5 $34.55   4.168%   $35.99   $35.99   $36.00   $36.00  
  Purchase #6 $129.89   5.116%   $136.5352   $136.54   $136.55   $136.50  
  Purchase #7 $66.50   9.788%   $73.009   $73.01   $73.00   $73.00  
  7 purchase totals = $752.31       $812.8432   $812.84   $812.90   $812.90