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 $87.36   8.683%   $94.9455   $94.95   $94.95   $94.90  
  Purchase #2 $176.61   11.519%   $196.9537   $196.95   $196.95   $197.00  
  Purchase #3 $246.71   4.581%   $258.0118   $258.01   $258.00   $258.00  
  Purchase #4 $141.62   9.259%   $154.7326   $154.73   $154.75   $154.70  
  Purchase #5 $119.48   5.853%   $126.4732   $126.47   $126.45   $126.50  
  Purchase #6 $28.87   4.686%   $30.2228   $30.22   $30.20   $30.20  
  Purchase #7 $28.63   3.196%   $29.545   $29.55   $29.55   $29.50  
  7 purchase totals = $829.28       $890.8846   $890.88   $890.85   $890.80