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 $59.49   6.734%   $63.4961   $63.50   $63.50   $63.50  
  Purchase #2 $173.77   4.872%   $182.2361   $182.24   $182.25   $182.20  
  Purchase #3 $196.96   4.243%   $205.317   $205.32   $205.30   $205.30  
  Purchase #4 $109.56   4.747%   $114.7608   $114.76   $114.75   $114.80  
  Purchase #5 $109.43   13.442%   $124.1396   $124.14   $124.15   $124.10  
  Purchase #6 $9.36   7.697%   $10.0804   $10.08   $10.10   $10.10  
  Purchase #7 $60.77   3.389%   $62.8295   $62.83   $62.85   $62.80  
  7 purchase totals = $719.34       $762.8595   $762.87   $762.90   $762.80