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 $174.92   11.617%   $195.2405   $195.24   $195.25   $195.20  
  Purchase #2 $175.87   10.850%   $194.9519   $194.95   $194.95   $195.00  
  Purchase #3 $208.86   3.720%   $216.6296   $216.63   $216.65   $216.60  
  Purchase #4 $148.47   3.516%   $153.6902   $153.69   $153.70   $153.70  
  Purchase #5 $162.88   6.490%   $173.4509   $173.45   $173.45   $173.50  
  Purchase #6 $15.64   9.635%   $17.1469   $17.15   $17.15   $17.10  
  Purchase #7 $34.73   6.185%   $36.8781   $36.88   $36.90   $36.90  
  7 purchase totals = $921.37       $987.9881   $987.99   $988.05   $988.00