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 $24.28   7.199%   $26.0279   $26.03   $26.05   $26.00  
  Purchase #2 $216.34   8.497%   $234.7224   $234.72   $234.70   $234.70  
  Purchase #3 $59.60   10.542%   $65.883   $65.88   $65.90   $65.90  
  Purchase #4 $98.61   3.699%   $102.2576   $102.26   $102.25   $102.30  
  Purchase #5 $86.80   10.685%   $96.0746   $96.07   $96.05   $96.10  
  Purchase #6 $90.38   8.218%   $97.8074   $97.81   $97.80   $97.80  
  Purchase #7 $88.86   5.368%   $93.63   $93.63   $93.65   $93.60  
  7 purchase totals = $664.87       $716.4029   $716.40   $716.40   $716.40