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 $60.45   4.378%   $63.0965   $63.10   $63.10   $63.10  
  Purchase #2 $151.43   11.204%   $168.3962   $168.40   $168.40   $168.40  
  Purchase #3 $62.94   12.628%   $70.8881   $70.89   $70.90   $70.90  
  Purchase #4 $125.84   7.816%   $135.6757   $135.68   $135.70   $135.70  
  Purchase #5 $117.34   3.690%   $121.6698   $121.67   $121.65   $121.70  
  Purchase #6 $211.85   12.218%   $237.7338   $237.73   $237.75   $237.70  
  Purchase #7 $148.83   11.215%   $165.5213   $165.52   $165.50   $165.50  
  7 purchase totals = $878.68       $962.9814   $962.99   $963.00   $963.00