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 $61.77   4.405%   $64.491   $64.49   $64.50   $64.50  
  Purchase #2 $161.53   3.517%   $167.211   $167.21   $167.20   $167.20  
  Purchase #3 $102.82   6.359%   $109.3583   $109.36   $109.35   $109.40  
  Purchase #4 $186.76   7.597%   $200.9482   $200.95   $200.95   $200.90  
  Purchase #5 $68.71   11.793%   $76.813   $76.81   $76.80   $76.80  
  Purchase #6 $202.47   5.246%   $213.0916   $213.09   $213.10   $213.10  
  Purchase #7 $249.86   13.158%   $282.7366   $282.74   $282.75   $282.70  
  7 purchase totals = $1,033.92       $1,114.6497   $1,114.65   $1,114.65   $1,114.60