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 $185.63   8.524%   $201.4531   $201.45   $201.45   $201.50  
  Purchase #2 $23.37   3.473%   $24.1816   $24.18   $24.20   $24.20  
  Purchase #3 $167.54   5.131%   $176.1365   $176.14   $176.15   $176.10  
  Purchase #4 $28.91   6.591%   $30.8155   $30.82   $30.80   $30.80  
  Purchase #5 $250.93   4.185%   $261.4314   $261.43   $261.45   $261.40  
  Purchase #6 $190.74   12.289%   $214.18   $214.18   $214.20   $214.20  
  Purchase #7 $202.73   10.338%   $223.6882   $223.69   $223.70   $223.70  
  7 purchase totals = $1,049.85       $1,131.8863   $1,131.89   $1,131.95   $1,131.90