woocommerce/plugins/woocommerce-blocks/packages/checkout/components/totals/taxes/style.scss

.wc-block-components-totals-item.wc-block-components-totals-taxes__grouped-rate {
	margin: $gap-smallest 0;
	&:first-child {
		margin-top: 0;
	}

	&:last-child {
		margin-bottom: 0;
	}
}