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 $92.28   3.720%   $95.7128   $95.71   $95.70   $95.70  
  Purchase #2 $232.92   12.464%   $261.9511   $261.95   $261.95   $262.00  
  Purchase #3 $238.97   3.387%   $247.0639   $247.06   $247.05   $247.10  
  Purchase #4 $55.47   10.309%   $61.1884   $61.19   $61.20   $61.20  
  Purchase #5 $214.60   8.477%   $232.7916   $232.79   $232.80   $232.80  
  Purchase #6 $231.87   9.271%   $253.3667   $253.37   $253.35   $253.40  
  Purchase #7 $161.51   13.522%   $183.3494   $183.35   $183.35   $183.30  
  7 purchase totals = $1,227.62       $1,335.4239   $1,335.42   $1,335.40   $1,335.50