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 $234.83   11.570%   $261.9998   $262.00   $262.00   $262.00  
  Purchase #2 $232.40   3.805%   $241.2428   $241.24   $241.25   $241.20  
  Purchase #3 $116.45   8.280%   $126.0921   $126.09   $126.10   $126.10  
  Purchase #4 $15.86   5.383%   $16.7137   $16.71   $16.70   $16.70  
  Purchase #5 $102.85   10.763%   $113.9197   $113.92   $113.90   $113.90  
  Purchase #6 $23.81   3.826%   $24.721   $24.72   $24.70   $24.70  
  Purchase #7 $100.55   10.764%   $111.3732   $111.37   $111.35   $111.40  
  7 purchase totals = $826.75       $896.0623   $896.05   $896.00   $896.00