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 $216.43   3.655%   $224.3405   $224.34   $224.35   $224.30  
  Purchase #2 $192.99   11.482%   $215.1491   $215.15   $215.15   $215.10  
  Purchase #3 $248.34   13.715%   $282.3998   $282.40   $282.40   $282.40  
  Purchase #4 $126.90   6.819%   $135.5533   $135.55   $135.55   $135.60  
  Purchase #5 $79.43   7.214%   $85.1601   $85.16   $85.15   $85.20  
  Purchase #6 $221.98   11.752%   $248.0671   $248.07   $248.05   $248.10  
  Purchase #7 $216.42   11.451%   $241.2023   $241.20   $241.20   $241.20  
  7 purchase totals = $1,302.49       $1,431.8722   $1,431.87   $1,431.85   $1,431.90