WordPress at a glance
action is not described

woocommerce_after_calculate_totals action-hook . WC 1.0

Usage

add_action( 'woocommerce_after_calculate_totals', 'action_function_name_4445' );
function action_function_name_4445( $that ){
	// action...
}
$that
-

Where the hook is called

WC_Cart::calculate_totals()
woocommerce_after_calculate_totals
woocommerce/includes/class-wc-cart.php 1230
do_action( 'woocommerce_after_calculate_totals', $this );

Where the hook is used (in WC core)

includes/class-wc-cart-session.php 50
add_action( 'woocommerce_after_calculate_totals', array( $this, 'set_session' ) );