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	$98.50	5.449%	$103.8673	$103.87	$103.85	$103.90
Purchase #2	$230.36	11.125%	$255.9876	$255.99	$256.00	$256.00
Purchase #3	$192.99	9.636%	$211.5865	$211.59	$211.60	$211.60
Purchase #4	$231.98	3.739%	$240.6537	$240.65	$240.65	$240.70
Purchase #5	$98.69	13.419%	$111.9332	$111.93	$111.95	$111.90
Purchase #6	$209.52	12.848%	$236.4391	$236.44	$236.45	$236.40
Purchase #7	$146.59	5.228%	$154.2537	$154.25	$154.25	$154.30
7 purchase totals =	$1,208.63		$1,314.7211	$1,314.72	$1,314.75	$1,314.80