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 $59.76   5.336%   $62.9488   $62.95   $62.95   $62.90  
  Purchase #2 $92.92   9.343%   $101.6015   $101.60   $101.60   $101.60  
  Purchase #3 $117.31   7.552%   $126.1693   $126.17   $126.15   $126.20  
  Purchase #4 $200.25   10.850%   $221.9771   $221.98   $222.00   $222.00  
  Purchase #5 $29.53   11.539%   $32.9375   $32.94   $32.95   $32.90  
  Purchase #6 $127.66   10.465%   $141.0196   $141.02   $141.00   $141.00  
  Purchase #7 $238.49   3.531%   $246.9111   $246.91   $246.90   $246.90  
  7 purchase totals = $865.92       $933.5649   $933.57   $933.55   $933.50