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With the release of Magento 1.7, changing currency symbols has become much easier. All currency symbols can be adjusted in the backend and no coding is required. Simply follow the below steps:
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Sometimes the default currency symbols in Magento aren't ideal.
1) Define the currencies you would like to use in your store under System > Configuration > General > Currency Setup > Allowed Currencies.
2) Go to System > Manage Currency > Symbols and update symbols as desired.
That’s it, nice and easy!