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 $43.88   6.518%   $46.7401   $46.74   $46.75   $46.70  
  Purchase #2 $236.28   10.874%   $261.9731   $261.97   $261.95   $262.00  
  Purchase #3 $69.83   6.843%   $74.6085   $74.61   $74.60   $74.60  
  Purchase #4 $32.40   9.731%   $35.5528   $35.55   $35.55   $35.60  
  Purchase #5 $192.29   12.225%   $215.7975   $215.80   $215.80   $215.80  
  Purchase #6 $71.97   8.671%   $78.2105   $78.21   $78.20   $78.20  
  Purchase #7 $200.97   9.511%   $220.0843   $220.08   $220.10   $220.10  
  7 purchase totals = $847.62       $932.9668   $932.96   $932.95   $933.00