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 $86.97   9.857%   $95.5426   $95.54   $95.55   $95.50  
  Purchase #2 $89.95   7.520%   $96.7142   $96.71   $96.70   $96.70  
  Purchase #3 $177.36   13.562%   $201.4136   $201.41   $201.40   $201.40  
  Purchase #4 $190.27   12.158%   $213.403   $213.40   $213.40   $213.40  
  Purchase #5 $106.87   7.264%   $114.633   $114.63   $114.65   $114.60  
  Purchase #6 $15.31   4.106%   $15.9386   $15.94   $15.95   $15.90  
  Purchase #7 $110.64   7.223%   $118.6315   $118.63   $118.65   $118.60  
  7 purchase totals = $777.37       $856.2765   $856.26   $856.30   $856.10