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 $86.60   11.556%   $96.6075   $96.61   $96.60   $96.60  
  Purchase #2 $144.26   13.794%   $164.1592   $164.16   $164.15   $164.20  
  Purchase #3 $102.90   10.841%   $114.0554   $114.06   $114.05   $114.10  
  Purchase #4 $198.93   4.596%   $208.0728   $208.07   $208.05   $208.10  
  Purchase #5 $14.97   7.431%   $16.0824   $16.08   $16.10   $16.10  
  Purchase #6 $13.54   3.588%   $14.0258   $14.03   $14.05   $14.00  
  Purchase #7 $234.91   7.809%   $253.2541   $253.25   $253.25   $253.30  
  7 purchase totals = $796.11       $866.2572   $866.26   $866.25   $866.40