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 $59.51   4.768%   $62.3474   $62.35   $62.35   $62.30  
  Purchase #2 $200.70   3.759%   $208.2443   $208.24   $208.25   $208.20  
  Purchase #3 $31.68   12.780%   $35.7287   $35.73   $35.75   $35.70  
  Purchase #4 $145.65   8.575%   $158.1395   $158.14   $158.15   $158.10  
  Purchase #5 $135.91   6.725%   $145.0499   $145.05   $145.05   $145.00  
  Purchase #6 $42.75   13.628%   $48.576   $48.58   $48.60   $48.60  
  Purchase #7 $109.42   8.680%   $118.9177   $118.92   $118.90   $118.90  
  7 purchase totals = $725.62       $777.0035   $777.01   $777.05   $776.80