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 $58.56   11.192%   $65.114   $65.11   $65.10   $65.10  
  Purchase #2 $207.33   13.161%   $234.6167   $234.62   $234.60   $234.60  
  Purchase #3 $192.57   8.105%   $208.1778   $208.18   $208.20   $208.20  
  Purchase #4 $248.38   4.566%   $259.721   $259.72   $259.70   $259.70  
  Purchase #5 $119.60   4.465%   $124.9401   $124.94   $124.95   $124.90  
  Purchase #6 $36.49   7.600%   $39.2632   $39.26   $39.25   $39.30  
  Purchase #7 $125.65   12.164%   $140.9341   $140.93   $140.95   $140.90  
  7 purchase totals = $988.58       $1,072.7669   $1,072.76   $1,072.75   $1,072.70