.data() doesn't convert '10.00' to number.

[gersonk]

<span id="a" data-value='10.00'>
<span id="b" data-value='10.01'>

  $("#a").data("value"); // returns "10.00" (string)
  $("#b").data("value"); // returns 10.01 (number)

[dmethvin]

Every attempt is made to convert the string to a JavaScript value (this includes booleans, numbers, objects, arrays, and null). A value is only converted to a number if doing so doesn't change the value's representation. For example, "1E02" and "100.000" are equivalent as numbers (numeric value 100) but converting them would alter their representation so they are left as strings. The string value "100" is converted to the number 100.

​http://api.jquery.com/data/