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 $85.37   13.461%   $96.8617   $96.86   $96.85   $96.90  
  Purchase #2 $59.75   5.610%   $63.102   $63.10   $63.10   $63.10  
  Purchase #3 $64.80   7.674%   $69.7728   $69.77   $69.75   $69.80  
  Purchase #4 $215.64   8.680%   $234.3576   $234.36   $234.35   $234.40  
  Purchase #5 $224.74   12.739%   $253.3696   $253.37   $253.35   $253.40  
  Purchase #6 $164.83   8.318%   $178.5406   $178.54   $178.55   $178.50  
  Purchase #7 $49.42   13.671%   $56.1762   $56.18   $56.20   $56.20  
  7 purchase totals = $864.55       $952.1805   $952.18   $952.15   $952.30