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 $114.42   8.322%   $123.942   $123.94   $123.95   $123.90  
  Purchase #2 $14.49   3.323%   $14.9715   $14.97   $14.95   $15.00  
  Purchase #3 $32.82   10.835%   $36.376   $36.38   $36.40   $36.40  
  Purchase #4 $50.25   7.567%   $54.0524   $54.05   $54.05   $54.10  
  Purchase #5 $226.95   9.513%   $248.5398   $248.54   $248.55   $248.50  
  Purchase #6 $156.73   3.177%   $161.7093   $161.71   $161.70   $161.70  
  Purchase #7 $80.49   4.285%   $83.939   $83.94   $83.95   $83.90  
  7 purchase totals = $676.15       $723.5300   $723.53   $723.55   $723.50