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 $140.68   3.770%   $145.9836   $145.98   $146.00   $146.00  
  Purchase #2 $84.67   11.723%   $94.5959   $94.60   $94.60   $94.60  
  Purchase #3 $24.56   5.673%   $25.9533   $25.95   $25.95   $26.00  
  Purchase #4 $145.44   11.300%   $161.8747   $161.87   $161.85   $161.90  
  Purchase #5 $222.94   10.229%   $245.7445   $245.74   $245.75   $245.70  
  Purchase #6 $34.34   8.422%   $37.2321   $37.23   $37.25   $37.20  
  Purchase #7 $46.64   4.247%   $48.6208   $48.62   $48.60   $48.60  
  7 purchase totals = $699.27       $760.0049   $759.99   $760.00   $760.00