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 $62.76   10.778%   $69.5243   $69.52   $69.50   $69.50  
  Purchase #2 $119.78   10.483%   $132.3365   $132.34   $132.35   $132.30  
  Purchase #3 $19.59   9.630%   $21.4765   $21.48   $21.50   $21.50  
  Purchase #4 $191.27   11.329%   $212.939   $212.94   $212.95   $212.90  
  Purchase #5 $142.48   8.289%   $154.2902   $154.29   $154.30   $154.30  
  Purchase #6 $40.93   6.260%   $43.4922   $43.49   $43.50   $43.50  
  Purchase #7 $122.90   5.171%   $129.2552   $129.26   $129.25   $129.30  
  7 purchase totals = $699.71       $763.3139   $763.32   $763.35   $763.30