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 $241.51   8.146%   $261.1834   $261.18   $261.20   $261.20  
  Purchase #2 $214.54   4.757%   $224.7457   $224.75   $224.75   $224.70  
  Purchase #3 $60.42   4.430%   $63.0966   $63.10   $63.10   $63.10  
  Purchase #4 $230.59   13.724%   $262.2362   $262.24   $262.25   $262.20  
  Purchase #5 $96.38   8.276%   $104.3564   $104.36   $104.35   $104.40  
  Purchase #6 $131.72   11.458%   $146.8125   $146.81   $146.80   $146.80  
  Purchase #7 $56.74   10.117%   $62.4804   $62.48   $62.50   $62.50  
  7 purchase totals = $1,031.90       $1,124.9112   $1,124.92   $1,124.95   $1,124.90