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	$114.44	7.811%	$123.3789	$123.38	$123.40	$123.40
Purchase #2	$118.73	11.161%	$131.9815	$131.98	$132.00	$132.00
Purchase #3	$21.45	11.163%	$23.8445	$23.84	$23.85	$23.80
Purchase #4	$178.71	11.568%	$199.3832	$199.38	$199.40	$199.40
Purchase #5	$65.59	12.501%	$73.7894	$73.79	$73.80	$73.80
Purchase #6	$104.52	6.326%	$111.1319	$111.13	$111.15	$111.10
Purchase #7	$51.81	5.466%	$54.6419	$54.64	$54.65	$54.60
7 purchase totals =	$655.25		$718.1513	$718.14	$718.25	$718.10