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 $41.50   7.342%   $44.5469   $44.55   $44.55   $44.50  
  Purchase #2 $233.85   6.769%   $249.6793   $249.68   $249.70   $249.70  
  Purchase #3 $47.52   8.272%   $51.4509   $51.45   $51.45   $51.50  
  Purchase #4 $153.94   11.565%   $171.7432   $171.74   $171.75   $171.70  
  Purchase #5 $232.77   8.798%   $253.2491   $253.25   $253.25   $253.20  
  Purchase #6 $101.66   12.725%   $114.5962   $114.60   $114.60   $114.60  
  Purchase #7 $24.95   7.575%   $26.84   $26.84   $26.85   $26.80  
  7 purchase totals = $836.19       $912.1056   $912.11   $912.15   $912.00