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	$154.58	11.138%	$171.7971	$171.80	$171.80	$171.80
Purchase #2	$34.70	11.556%	$38.7099	$38.71	$38.70	$38.70
Purchase #3	$106.64	4.530%	$111.4708	$111.47	$111.45	$111.50
Purchase #4	$144.60	6.674%	$154.2506	$154.25	$154.25	$154.30
Purchase #5	$249.59	11.448%	$278.1631	$278.16	$278.15	$278.20
Purchase #6	$45.41	13.255%	$51.4291	$51.43	$51.45	$51.40
Purchase #7	$128.52	10.303%	$141.7614	$141.76	$141.75	$141.80
7 purchase totals =	$864.04		$947.5820	$947.58	$947.55	$947.70