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 $58.37   8.787%   $63.499   $63.50   $63.50   $63.50  
  Purchase #2 $205.70   11.552%   $229.4625   $229.46   $229.45   $229.50  
  Purchase #3 $107.91   13.440%   $122.4131   $122.41   $122.40   $122.40  
  Purchase #4 $143.29   12.526%   $161.2385   $161.24   $161.25   $161.20  
  Purchase #5 $108.69   13.321%   $123.1686   $123.17   $123.15   $123.20  
  Purchase #6 $180.94   5.253%   $190.4448   $190.44   $190.45   $190.40  
  Purchase #7 $55.64   11.433%   $62.0013   $62.00   $62.00   $62.00  
  7 purchase totals = $860.54       $952.2278   $952.22   $952.20   $952.20