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 $241.66   5.424%   $254.7676   $254.77   $254.75   $254.80  
  Purchase #2 $238.71   9.519%   $261.4328   $261.43   $261.45   $261.40  
  Purchase #3 $62.68   8.720%   $68.1457   $68.15   $68.15   $68.10  
  Purchase #4 $9.81   13.858%   $11.1695   $11.17   $11.15   $11.20  
  Purchase #5 $12.76   12.750%   $14.3869   $14.39   $14.40   $14.40  
  Purchase #6 $236.65   4.651%   $247.6566   $247.66   $247.65   $247.70  
  Purchase #7 $234.63   4.721%   $245.7069   $245.71   $245.70   $245.70  
  7 purchase totals = $1,036.90       $1,103.2660   $1,103.28   $1,103.25   $1,103.30