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	$100.99	10.683%	$111.7788	$111.78	$111.80	$111.80
Purchase #2	$28.56	9.767%	$31.3495	$31.35	$31.35	$31.30
Purchase #3	$31.39	4.173%	$32.6999	$32.70	$32.70	$32.70
Purchase #4	$30.77	5.207%	$32.3722	$32.37	$32.35	$32.40
Purchase #5	$179.39	11.844%	$200.637	$200.64	$200.65	$200.60
Purchase #6	$11.49	11.757%	$12.8409	$12.84	$12.85	$12.80
Purchase #7	$163.35	13.622%	$185.6015	$185.60	$185.60	$185.60
7 purchase totals =	$545.94		$607.2798	$607.28	$607.30	$607.20