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 $106.38   7.118%   $113.9521   $113.95   $113.95   $114.00  
  Purchase #2 $213.80   13.472%   $242.6031   $242.60   $242.60   $242.60  
  Purchase #3 $67.25   13.493%   $76.324   $76.32   $76.30   $76.30  
  Purchase #4 $124.38   8.515%   $134.971   $134.97   $134.95   $135.00  
  Purchase #5 $74.26   9.244%   $81.1246   $81.12   $81.10   $81.10  
  Purchase #6 $48.91   6.799%   $52.2354   $52.24   $52.25   $52.20  
  Purchase #7 $91.71   3.506%   $94.9254   $94.93   $94.95   $94.90  
  7 purchase totals = $726.69       $796.1356   $796.13   $796.10   $796.10