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 $57.96   7.433%   $62.2682   $62.27   $62.25   $62.30  
  Purchase #2 $46.70   4.262%   $48.6904   $48.69   $48.70   $48.70  
  Purchase #3 $230.31   13.573%   $261.57   $261.57   $261.55   $261.60  
  Purchase #4 $197.74   5.452%   $208.5208   $208.52   $208.50   $208.50  
  Purchase #5 $57.79   3.374%   $59.7398   $59.74   $59.75   $59.70  
  Purchase #6 $201.87   8.863%   $219.7617   $219.76   $219.75   $219.80  
  Purchase #7 $71.94   6.277%   $76.4557   $76.46   $76.45   $76.50  
  7 purchase totals = $864.31       $937.0066   $937.01   $936.95   $937.10