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 $47.41   13.256%   $53.6947   $53.69   $53.70   $53.70  
  Purchase #2 $192.43   10.106%   $211.877   $211.88   $211.90   $211.90  
  Purchase #3 $84.74   8.646%   $92.0666   $92.07   $92.05   $92.10  
  Purchase #4 $127.65   3.731%   $132.4126   $132.41   $132.40   $132.40  
  Purchase #5 $170.94   11.451%   $190.5143   $190.51   $190.50   $190.50  
  Purchase #6 $58.84   6.643%   $62.7487   $62.75   $62.75   $62.70  
  Purchase #7 $39.63   7.813%   $42.7263   $42.73   $42.75   $42.70  
  7 purchase totals = $721.64       $786.0402   $786.04   $786.05   $786.00