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 $244.37   5.468%   $257.7322   $257.73   $257.75   $257.70  
  Purchase #2 $181.87   11.164%   $202.174   $202.17   $202.15   $202.20  
  Purchase #3 $218.95   8.654%   $237.8979   $237.90   $237.90   $237.90  
  Purchase #4 $249.79   6.336%   $265.6167   $265.62   $265.60   $265.60  
  Purchase #5 $107.79   6.366%   $114.6519   $114.65   $114.65   $114.70  
  Purchase #6 $127.83   11.768%   $142.873   $142.87   $142.85   $142.90  
  Purchase #7 $44.89   5.545%   $47.3792   $47.38   $47.40   $47.40  
  7 purchase totals = $1,175.49       $1,268.3249   $1,268.32   $1,268.30   $1,268.40