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 $208.63   3.510%   $215.9529   $215.95   $215.95   $216.00  
  Purchase #2 $35.61   6.753%   $38.0147   $38.01   $38.00   $38.00  
  Purchase #3 $75.99   4.617%   $79.4985   $79.50   $79.50   $79.50  
  Purchase #4 $66.38   10.334%   $73.2397   $73.24   $73.25   $73.20  
  Purchase #5 $47.25   7.799%   $50.935   $50.94   $50.95   $50.90  
  Purchase #6 $17.34   3.535%   $17.953   $17.95   $17.95   $18.00  
  Purchase #7 $244.84   4.709%   $256.3695   $256.37   $256.35   $256.40  
  7 purchase totals = $696.04       $731.9633   $731.96   $731.95   $732.00