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 $208.51   7.865%   $224.9093   $224.91   $224.90   $224.90  
  Purchase #2 $140.28   3.823%   $145.6429   $145.64   $145.65   $145.60  
  Purchase #3 $25.53   3.509%   $26.4258   $26.43   $26.45   $26.40  
  Purchase #4 $15.34   4.323%   $16.0031   $16.00   $16.00   $16.00  
  Purchase #5 $110.94   10.491%   $122.5787   $122.58   $122.60   $122.60  
  Purchase #6 $48.87   12.727%   $55.0897   $55.09   $55.10   $55.10  
  Purchase #7 $161.57   7.679%   $173.977   $173.98   $174.00   $174.00  
  7 purchase totals = $711.04       $764.6265   $764.63   $764.70   $764.60