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 $23.92   8.858%   $26.0388   $26.04   $26.05   $26.00  
  Purchase #2 $175.27   6.650%   $186.9255   $186.93   $186.95   $186.90  
  Purchase #3 $21.68   5.157%   $22.798   $22.80   $22.80   $22.80  
  Purchase #4 $206.94   10.251%   $228.1534   $228.15   $228.15   $228.20  
  Purchase #5 $22.26   5.408%   $23.4638   $23.46   $23.45   $23.50  
  Purchase #6 $197.64   8.260%   $213.9651   $213.97   $213.95   $214.00  
  Purchase #7 $236.76   5.269%   $249.2349   $249.23   $249.25   $249.20  
  7 purchase totals = $884.47       $950.5795   $950.58   $950.60   $950.60