Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$104.84	6.177%	$111.316	$111.32	$111.30	$111.30
Purchase #2	$72.83	6.530%	$77.5858	$77.59	$77.60	$77.60
Purchase #3	$143.49	7.426%	$154.1456	$154.15	$154.15	$154.10
Purchase #4	$165.30	4.411%	$172.5914	$172.59	$172.60	$172.60
Purchase #5	$43.71	10.463%	$48.2834	$48.28	$48.30	$48.30
Purchase #6	$162.80	12.377%	$182.9498	$182.95	$182.95	$182.90
Purchase #7	$96.78	8.288%	$104.8011	$104.80	$104.80	$104.80
7 purchase totals =	$789.75		$851.6731	$851.68	$851.70	$851.60