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 $118.81   13.197%   $134.4894   $134.49   $134.50   $134.50  
  Purchase #2 $61.37   3.197%   $63.332   $63.33   $63.35   $63.30  
  Purchase #3 $71.33   3.416%   $73.7666   $73.77   $73.75   $73.80  
  Purchase #4 $90.68   8.553%   $98.4359   $98.44   $98.45   $98.40  
  Purchase #5 $45.70   6.299%   $48.5786   $48.58   $48.60   $48.60  
  Purchase #6 $201.50   3.521%   $208.5948   $208.59   $208.60   $208.60  
  Purchase #7 $92.93   10.589%   $102.7704   $102.77   $102.75   $102.80  
  7 purchase totals = $682.32       $729.9677   $729.97   $730.00   $730.00