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	$11.78	4.445%	$12.3036	$12.30	$12.30	$12.30
Purchase #2	$118.96	10.666%	$131.6483	$131.65	$131.65	$131.60
Purchase #3	$244.49	10.237%	$269.5184	$269.52	$269.50	$269.50
Purchase #4	$204.38	5.115%	$214.834	$214.83	$214.85	$214.80
Purchase #5	$163.41	5.545%	$172.4711	$172.47	$172.45	$172.50
Purchase #6	$219.40	10.203%	$241.7854	$241.79	$241.80	$241.80
Purchase #7	$157.41	7.172%	$168.6994	$168.70	$168.70	$168.70
7 purchase totals =	$1,119.83		$1,211.2602	$1,211.26	$1,211.25	$1,211.20