In Woocommerce, I\'ve set the number of decimal to 7 on in Woocommerce general settings, so I can display the product price like this $0.0453321>
If you want to change cart total only at cart and checkout page then you need to copy template in your theme
First copy 2 files from woocommerce plugin template to your theme .
1) Copy plugins\woocommerce\templates\cart\cart-totals.php to your-theme-folder\woocommerce\cart\cart-totals.php
2) Copy plugins\woocommerce\templates\checkout\review-order.php to your-theme-folder\woocommerce\checkout\review-order.php
And in both files find the wc_cart_totals_order_total_html() comment this code and put below code instead.
$args=array('decimals'=> 2);
echo wc_price(WC()->cart->total,$args);
This code is tested and its working fine.Hope it will help you as well.