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 $83.77   13.666%   $95.218   $95.22   $95.20   $95.20  
  Purchase #2 $110.70   3.132%   $114.1671   $114.17   $114.15   $114.20  
  Purchase #3 $148.60   10.618%   $164.3783   $164.38   $164.40   $164.40  
  Purchase #4 $157.91   5.549%   $166.6724   $166.67   $166.65   $166.70  
  Purchase #5 $248.42   5.670%   $262.5054   $262.51   $262.50   $262.50  
  Purchase #6 $226.68   8.138%   $245.1272   $245.13   $245.15   $245.10  
  Purchase #7 $232.49   10.200%   $256.204   $256.20   $256.20   $256.20  
  7 purchase totals = $1,208.57       $1,304.2724   $1,304.28   $1,304.25   $1,304.30