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 $109.49   4.462%   $114.3754   $114.38   $114.40   $114.40  
  Purchase #2 $139.89   10.262%   $154.2455   $154.25   $154.25   $154.20  
  Purchase #3 $168.76   4.602%   $176.5263   $176.53   $176.55   $176.50  
  Purchase #4 $87.41   9.222%   $95.471   $95.47   $95.45   $95.50  
  Purchase #5 $88.48   8.134%   $95.677   $95.68   $95.70   $95.70  
  Purchase #6 $111.54   6.647%   $118.9541   $118.95   $118.95   $119.00  
  Purchase #7 $247.98   9.149%   $270.6677   $270.67   $270.65   $270.70  
  7 purchase totals = $953.55       $1,025.9170   $1,025.93   $1,025.95   $1,026.00