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 $212.83   5.457%   $224.4441   $224.44   $224.45   $224.40  
  Purchase #2 $22.99   13.859%   $26.1762   $26.18   $26.20   $26.20  
  Purchase #3 $70.27   9.398%   $76.874   $76.87   $76.85   $76.90  
  Purchase #4 $35.41   6.649%   $37.7644   $37.76   $37.75   $37.80  
  Purchase #5 $47.66   5.230%   $50.1526   $50.15   $50.15   $50.20  
  Purchase #6 $62.91   11.577%   $70.1931   $70.19   $70.20   $70.20  
  Purchase #7 $81.73   5.166%   $85.9522   $85.95   $85.95   $86.00  
  7 purchase totals = $533.80       $571.5566   $571.54   $571.55   $571.70