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 $118.79   5.753%   $125.624   $125.62   $125.60   $125.60  
  Purchase #2 $183.97   13.793%   $209.345   $209.35   $209.35   $209.30  
  Purchase #3 $114.99   7.238%   $123.313   $123.31   $123.30   $123.30  
  Purchase #4 $81.26   5.792%   $85.9666   $85.97   $85.95   $86.00  
  Purchase #5 $164.25   8.131%   $177.6052   $177.61   $177.60   $177.60  
  Purchase #6 $112.73   10.577%   $124.6535   $124.65   $124.65   $124.70  
  Purchase #7 $129.40   5.123%   $136.0292   $136.03   $136.05   $136.00  
  7 purchase totals = $905.39       $982.5365   $982.54   $982.50   $982.50