Find out if the reimbursements are under accountable plan or nonaccountable plan. Under accountable plan, it is not reported as income and you can't claim deduction on schedule A under Employee Business Expenses.
Under nonaccountable plan, these are added to your W2 income. This income is also subject to FICA (ss and medicare) taxes. You can deduct these expenses only if you itemize your deductions that is if you file schedule A (Form 1040). And you can deduct only the expenses that are more than 2% of your AGI (adjusted gross income).
Also you will itemize your deductions only if your itemized deductions are more than your standard deduction. Standard deduction is $5,350 for single and $10,700 for Married Filing Jointly.
What ever your employer is holding as federal or state income tax, is not your actual tax. It can be more than or less than your actual tax. You will know your actual tax when you complete your tax return for the year. If withholdings are more than the tax as per the return, you will get a refund.