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 $195.68   13.580%   $222.2533   $222.25   $222.25   $222.30  
  Purchase #2 $27.43   10.255%   $30.2429   $30.24   $30.25   $30.20  
  Purchase #3 $97.55   12.455%   $109.6999   $109.70   $109.70   $109.70  
  Purchase #4 $165.73   10.600%   $183.2974   $183.30   $183.30   $183.30  
  Purchase #5 $62.59   3.827%   $64.9853   $64.99   $65.00   $65.00  
  Purchase #6 $83.27   12.302%   $93.5139   $93.51   $93.50   $93.50  
  Purchase #7 $26.93   5.531%   $28.4195   $28.42   $28.40   $28.40  
  7 purchase totals = $659.18       $732.4122   $732.41   $732.40   $732.40