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 $107.48   6.569%   $114.5404   $114.54   $114.55   $114.50  
  Purchase #2 $126.61   7.147%   $135.6588   $135.66   $135.65   $135.70  
  Purchase #3 $220.48   9.316%   $241.0199   $241.02   $241.00   $241.00  
  Purchase #4 $168.99   3.330%   $174.6174   $174.62   $174.60   $174.60  
  Purchase #5 $108.65   8.573%   $117.9646   $117.96   $117.95   $118.00  
  Purchase #6 $242.54   5.318%   $255.4383   $255.44   $255.45   $255.40  
  Purchase #7 $11.69   10.543%   $12.9225   $12.92   $12.90   $12.90  
  7 purchase totals = $986.44       $1,052.1619   $1,052.16   $1,052.10   $1,052.10