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 $61.62   11.473%   $68.6897   $68.69   $68.70   $68.70  
  Purchase #2 $206.82   4.863%   $216.8777   $216.88   $216.90   $216.90  
  Purchase #3 $10.34   13.510%   $11.7369   $11.74   $11.75   $11.70  
  Purchase #4 $58.47   4.259%   $60.9602   $60.96   $60.95   $61.00  
  Purchase #5 $247.52   11.149%   $275.116   $275.12   $275.10   $275.10  
  Purchase #6 $208.92   13.180%   $236.4557   $236.46   $236.45   $236.50  
  Purchase #7 $64.68   4.611%   $67.6624   $67.66   $67.65   $67.70  
  7 purchase totals = $858.37       $937.4986   $937.51   $937.50   $937.60