How can I change the resolution of a raster using GDAL?

You need to reproject the raster. For example, from an interactive Python shell:

from osgeo import gdal
help(gdal.ReprojectImage)

A Python example is provided in the test suite.

More complete documentation is provided for the C++ function GDALReprojectImage.

Use gdal.Warp function:

gdal.Warp('outputRaster.tif', 'inputRaster.tif', xRes=5, yRes=5)

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