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 $24.96   4.494%   $26.0817   $26.08   $26.10   $26.10  
  Purchase #2 $158.40   6.699%   $169.0112   $169.01   $169.00   $169.00  
  Purchase #3 $48.48   13.550%   $55.049   $55.05   $55.05   $55.00  
  Purchase #4 $81.34   7.527%   $87.4625   $87.46   $87.45   $87.50  
  Purchase #5 $111.70   4.411%   $116.6271   $116.63   $116.65   $116.60  
  Purchase #6 $44.64   5.182%   $46.9532   $46.95   $46.95   $47.00  
  Purchase #7 $195.55   6.706%   $208.6636   $208.66   $208.65   $208.70  
  7 purchase totals = $665.07       $709.8483   $709.84   $709.85   $709.90