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 $238.97   9.482%   $261.6291   $261.63   $261.65   $261.60  
  Purchase #2 $59.71   3.651%   $61.89   $61.89   $61.90   $61.90  
  Purchase #3 $149.70   9.649%   $164.1446   $164.14   $164.15   $164.10  
  Purchase #4 $77.32   7.787%   $83.3409   $83.34   $83.35   $83.30  
  Purchase #5 $188.33   5.465%   $198.6222   $198.62   $198.60   $198.60  
  Purchase #6 $173.73   9.722%   $190.62   $190.62   $190.60   $190.60  
  Purchase #7 $226.53   3.621%   $234.7327   $234.73   $234.75   $234.70  
  7 purchase totals = $1,114.29       $1,194.9795   $1,194.97   $1,195.00   $1,194.80