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 $88.26   6.676%   $94.1522   $94.15   $94.15   $94.20  
  Purchase #2 $191.42   13.731%   $217.7039   $217.70   $217.70   $217.70  
  Purchase #3 $13.76   6.841%   $14.7013   $14.70   $14.70   $14.70  
  Purchase #4 $130.63   3.268%   $134.899   $134.90   $134.90   $134.90  
  Purchase #5 $157.80   11.609%   $176.119   $176.12   $176.10   $176.10  
  Purchase #6 $137.61   6.722%   $146.8601   $146.86   $146.85   $146.90  
  Purchase #7 $136.95   10.274%   $151.0202   $151.02   $151.00   $151.00  
  7 purchase totals = $856.43       $935.4557   $935.45   $935.40   $935.50