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	$243.81	7.564%	$262.2518	$262.25	$262.25	$262.30
Purchase #2	$233.50	4.761%	$244.6169	$244.62	$244.60	$244.60
Purchase #3	$170.64	12.257%	$191.5553	$191.56	$191.55	$191.60
Purchase #4	$234.41	7.536%	$252.0751	$252.08	$252.10	$252.10
Purchase #5	$41.85	4.444%	$43.7098	$43.71	$43.70	$43.70
Purchase #6	$243.87	11.333%	$271.5078	$271.51	$271.50	$271.50
Purchase #7	$107.49	3.707%	$111.4747	$111.47	$111.45	$111.50
7 purchase totals =	$1,275.57		$1,377.1914	$1,377.20	$1,377.15	$1,377.30