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	$177.58	8.196%	$192.1345	$192.13	$192.15	$192.10
Purchase #2	$239.77	6.703%	$255.8418	$255.84	$255.85	$255.80
Purchase #3	$159.48	8.335%	$172.7727	$172.77	$172.75	$172.80
Purchase #4	$80.92	10.545%	$89.453	$89.45	$89.45	$89.50
Purchase #5	$212.95	5.832%	$225.3692	$225.37	$225.35	$225.40
Purchase #6	$199.43	9.177%	$217.7317	$217.73	$217.75	$217.70
Purchase #7	$115.76	3.283%	$119.5604	$119.56	$119.55	$119.60
7 purchase totals =	$1,185.89		$1,272.8633	$1,272.85	$1,272.85	$1,272.90