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 $71.84   3.854%   $74.6087   $74.61   $74.60   $74.60  
  Purchase #2 $195.57   6.819%   $208.9059   $208.91   $208.90   $208.90  
  Purchase #3 $69.38   6.169%   $73.6601   $73.66   $73.65   $73.70  
  Purchase #4 $170.53   7.857%   $183.9285   $183.93   $183.95   $183.90  
  Purchase #5 $58.96   11.873%   $65.9603   $65.96   $65.95   $66.00  
  Purchase #6 $248.36   10.164%   $273.6033   $273.60   $273.60   $273.60  
  Purchase #7 $206.33   7.265%   $221.3199   $221.32   $221.30   $221.30  
  7 purchase totals = $1,020.97       $1,101.9867   $1,101.99   $1,101.95   $1,102.00