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 $102.87   11.272%   $114.4655   $114.47   $114.45   $114.50  
  Purchase #2 $202.49   7.447%   $217.5694   $217.57   $217.55   $217.60  
  Purchase #3 $23.87   10.547%   $26.3876   $26.39   $26.40   $26.40  
  Purchase #4 $107.68   5.314%   $113.4021   $113.40   $113.40   $113.40  
  Purchase #5 $198.41   6.728%   $211.759   $211.76   $211.75   $211.80  
  Purchase #6 $240.54   12.350%   $270.2467   $270.25   $270.25   $270.20  
  Purchase #7 $143.68   4.339%   $149.9143   $149.91   $149.90   $149.90  
  7 purchase totals = $1,019.54       $1,103.7446   $1,103.75   $1,103.70   $1,103.80