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 $250.63   4.211%   $261.184   $261.18   $261.20   $261.20  
  Purchase #2 $176.45   8.620%   $191.66   $191.66   $191.65   $191.70  
  Purchase #3 $214.90   8.427%   $233.0096   $233.01   $233.00   $233.00  
  Purchase #4 $68.39   3.359%   $70.6872   $70.69   $70.70   $70.70  
  Purchase #5 $196.61   9.813%   $215.9033   $215.90   $215.90   $215.90  
  Purchase #6 $36.81   3.184%   $37.982   $37.98   $38.00   $38.00  
  Purchase #7 $115.94   7.371%   $124.4859   $124.49   $124.50   $124.50  
  7 purchase totals = $1,059.73       $1,134.9120   $1,134.91   $1,134.95   $1,135.00