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	$217.62	10.856%	$241.2448	$241.24	$241.25	$241.20
Purchase #2	$204.53	12.513%	$230.1228	$230.12	$230.10	$230.10
Purchase #3	$62.74	9.182%	$68.5008	$68.50	$68.50	$68.50
Purchase #4	$142.39	9.646%	$156.1249	$156.12	$156.10	$156.10
Purchase #5	$137.42	6.209%	$145.9524	$145.95	$145.95	$146.00
Purchase #6	$83.34	7.491%	$89.583	$89.58	$89.60	$89.60
Purchase #7	$145.28	4.721%	$152.1387	$152.14	$152.15	$152.10
7 purchase totals =	$993.32		$1,083.6674	$1,083.65	$1,083.65	$1,083.60