A charitable donation almost never changes your tax due or refund all by itself.  First, your donation does not count "dollar for dollar"--it is calculated by a percentage based on your tax bracket.  You need a LOT of other itemized deductions like mortgage interest or property taxes, medical expense, etc. to itemize and exceed your standard deduction.

Your itemized deductions have to be more than your standard deduction before you will see a change in your tax owed or tax refund.  The deductions you enter do not necessarily count “dollar for dollar;” many of them are subject to meeting  tough thresholds—medical expenses, job-related expenses, casualty and theft losses, for example, must meet thresholds that are pretty hard to reach.  The software program uses all the IRS rules that apply to the expenses you enter, and it tells you if you have enough to use your itemized deductions or if using the standard deduction is more advantageous for you. Here are the Standard Deductions for 2017

Your standard deduction lowers your taxable income.  It is not a refund 

2017 Standard Deductions

Single    $6350  (65 or older + $1550)

Married Filing Separately   $6350  (65 or older +  $1250)

Married Filing Jointly           $12,700  (65 or older + $1250@)

Head of Household $9350  (65 or older + $1550)