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	$99.38	5.147%	$104.4951	$104.50	$104.50	$104.50
Purchase #2	$111.93	4.326%	$116.7721	$116.77	$116.75	$116.80
Purchase #3	$114.99	10.428%	$126.9812	$126.98	$127.00	$127.00
Purchase #4	$144.38	7.254%	$154.8533	$154.85	$154.85	$154.90
Purchase #5	$204.68	12.759%	$230.7951	$230.80	$230.80	$230.80
Purchase #6	$97.35	6.367%	$103.5483	$103.55	$103.55	$103.50
Purchase #7	$233.99	10.751%	$259.1463	$259.15	$259.15	$259.10
7 purchase totals =	$1,006.70		$1,096.5914	$1,096.60	$1,096.60	$1,096.60