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 $43.68   7.283%   $46.8612   $46.86   $46.85   $46.90  
  Purchase #2 $182.44   6.829%   $194.8988   $194.90   $194.90   $194.90  
  Purchase #3 $228.77   9.380%   $250.2286   $250.23   $250.25   $250.20  
  Purchase #4 $234.84   5.862%   $248.6063   $248.61   $248.60   $248.60  
  Purchase #5 $105.66   8.105%   $114.2237   $114.22   $114.20   $114.20  
  Purchase #6 $69.62   7.231%   $74.6542   $74.65   $74.65   $74.70  
  Purchase #7 $132.54   8.444%   $143.7317   $143.73   $143.75   $143.70  
  7 purchase totals = $997.55       $1,073.2045   $1,073.20   $1,073.20   $1,073.20