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 $206.68   3.871%   $214.6806   $214.68   $214.70   $214.70  
  Purchase #2 $71.38   8.745%   $77.6222   $77.62   $77.60   $77.60  
  Purchase #3 $161.84   7.150%   $173.4116   $173.41   $173.40   $173.40  
  Purchase #4 $131.82   4.109%   $137.2365   $137.24   $137.25   $137.20  
  Purchase #5 $99.97   13.271%   $113.237   $113.24   $113.25   $113.20  
  Purchase #6 $220.71   6.514%   $235.087   $235.09   $235.10   $235.10  
  Purchase #7 $247.65   11.490%   $276.105   $276.11   $276.10   $276.10  
  7 purchase totals = $1,140.05       $1,227.3799   $1,227.39   $1,227.40   $1,227.30