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 $211.51   7.302%   $226.9545   $226.95   $226.95   $227.00  
  Purchase #2 $167.53   9.276%   $183.0701   $183.07   $183.05   $183.10  
  Purchase #3 $165.75   3.595%   $171.7087   $171.71   $171.70   $171.70  
  Purchase #4 $161.35   8.646%   $175.3003   $175.30   $175.30   $175.30  
  Purchase #5 $127.90   4.474%   $133.6222   $133.62   $133.60   $133.60  
  Purchase #6 $109.54   4.420%   $114.3817   $114.38   $114.40   $114.40  
  Purchase #7 $123.95   5.313%   $130.5355   $130.54   $130.55   $130.50  
  7 purchase totals = $1,067.53       $1,135.5730   $1,135.57   $1,135.55   $1,135.60