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 $82.47   4.265%   $85.9873   $85.99   $86.00   $86.00  
  Purchase #2 $176.31   12.193%   $197.8075   $197.81   $197.80   $197.80  
  Purchase #3 $119.94   13.710%   $136.3838   $136.38   $136.40   $136.40  
  Purchase #4 $239.46   3.776%   $248.502   $248.50   $248.50   $248.50  
  Purchase #5 $248.60   13.137%   $281.2586   $281.26   $281.25   $281.30  
  Purchase #6 $126.66   13.488%   $143.7439   $143.74   $143.75   $143.70  
  Purchase #7 $12.41   3.311%   $12.8209   $12.82   $12.80   $12.80  
  7 purchase totals = $1,005.85       $1,106.5040   $1,106.50   $1,106.50   $1,106.50