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 $218.82   7.370%   $234.947   $234.95   $234.95   $234.90  
  Purchase #2 $16.28   6.465%   $17.3325   $17.33   $17.35   $17.30  
  Purchase #3 $62.43   5.462%   $65.8399   $65.84   $65.85   $65.80  
  Purchase #4 $141.61   11.366%   $157.7054   $157.71   $157.70   $157.70  
  Purchase #5 $134.71   10.193%   $148.441   $148.44   $148.45   $148.40  
  Purchase #6 $207.67   4.208%   $216.4088   $216.41   $216.40   $216.40  
  Purchase #7 $83.73   12.809%   $94.455   $94.46   $94.45   $94.50  
  7 purchase totals = $865.25       $935.1296   $935.14   $935.15   $935.00