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 $41.39   5.558%   $43.6905   $43.69   $43.70   $43.70  
  Purchase #2 $196.46   10.382%   $216.8565   $216.86   $216.85   $216.90  
  Purchase #3 $20.40   6.858%   $21.799   $21.80   $21.80   $21.80  
  Purchase #4 $228.27   5.741%   $241.375   $241.38   $241.40   $241.40  
  Purchase #5 $192.64   13.614%   $218.866   $218.87   $218.85   $218.90  
  Purchase #6 $248.88   4.444%   $259.9402   $259.94   $259.95   $259.90  
  Purchase #7 $206.84   8.361%   $224.1339   $224.13   $224.15   $224.10  
  7 purchase totals = $1,134.88       $1,226.6611   $1,226.67   $1,226.70   $1,226.70