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 $85.63   13.217%   $96.9477   $96.95   $96.95   $96.90  
  Purchase #2 $96.98   10.603%   $107.2628   $107.26   $107.25   $107.30  
  Purchase #3 $224.39   9.496%   $245.6981   $245.70   $245.70   $245.70  
  Purchase #4 $36.45   3.611%   $37.7662   $37.77   $37.75   $37.80  
  Purchase #5 $89.77   9.245%   $98.0692   $98.07   $98.05   $98.10  
  Purchase #6 $107.68   6.546%   $114.7287   $114.73   $114.75   $114.70  
  Purchase #7 $10.91   13.126%   $12.342   $12.34   $12.35   $12.30  
  7 purchase totals = $651.81       $712.8147   $712.82   $712.80   $712.80