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	$163.52	5.496%	$172.5071	$172.51	$172.50	$172.50
Purchase #2	$230.91	10.833%	$255.9245	$255.92	$255.90	$255.90
Purchase #3	$52.77	7.183%	$56.5605	$56.56	$56.55	$56.60
Purchase #4	$132.99	4.250%	$138.6421	$138.64	$138.65	$138.60
Purchase #5	$137.86	10.558%	$152.4153	$152.42	$152.40	$152.40
Purchase #6	$244.85	11.550%	$273.1302	$273.13	$273.15	$273.10
Purchase #7	$12.84	9.558%	$14.0672	$14.07	$14.05	$14.10
7 purchase totals =	$975.74		$1,063.2469	$1,063.25	$1,063.20	$1,063.20