Grunt cssmin for .min.css files

Am using grunt and cssmin to minify my css.

However, in my css assets folder, I have some css that has a .min.css extension. So when I run grunt, only files with .css in my source folder will be minified to be in the build folder. Those files that have .min.css in the source folder will be found in the build folder, but the .min extension will be lost. ie bootstrap.min.css will become bootstrap.css

My Gruntfile.js is as below

module.exports = function(grunt) {

  // Project configuration.
  grunt.initConfig({
    pkg: grunt.file.readJSON('package.json'),
    uglify: {
      options: {
        banner: '/*! <%= pkg.name %> <%= grunt.template.today("yyyy-mm-dd") %> */\n'
      },
      build: {
        files: [{
            expand: true,
            src: '**/*.js',
            dest: 'resources/front/js',
            cwd: 'assets/front/js'
        }]
      }
    },
   cssmin: {
      minify: {
        expand: true,
        cwd: 'assets/front/css/',
        src: ['*.css', '*.min.css'],
        dest: 'resources/front/css/',
        ext: '.css'
      }
    }

    });

  // Load the plugin that provides the "uglify" task.
  grunt.loadNpmTasks('grunt-contrib-uglify');
  grunt.loadNpmTasks('grunt-contrib-cssmin');

  // Default task(s).
  grunt.registerTask('default', ['uglify','cssmin']);

};

Is there any way that the .min.css files can still be minified and be in the build folder and retain the correct '.min.css' extension?

EDIT

See this answer for the most control over file name renaming.

Try this:

cssmin: {
  minify: {
    files: [{
      expand: true,
      cwd: 'assets/front/css/',
      src: ['*.css', '!*.min.css'],
      dest: 'resources/front/css/',
      ext: '.css'
    }, {
      expand: true,
      cwd: 'assets/front/css/',
      src: ['*.min.css'],
      dest: 'resources/front/css/',
      ext: '.min.css'
    }]
  }
}

The first files block will minify only the *.css files and retain the .css extension of those files. The second files block will minify only the *.min.css files and retain the .min.css extension of those files.