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	$211.51	5.195%	$222.4979	$222.50	$222.50	$222.50
Purchase #2	$12.85	5.722%	$13.5853	$13.59	$13.60	$13.60
Purchase #3	$126.77	12.299%	$142.3614	$142.36	$142.35	$142.40
Purchase #4	$154.75	5.783%	$163.6992	$163.70	$163.70	$163.70
Purchase #5	$242.32	9.335%	$264.9406	$264.94	$264.95	$264.90
Purchase #6	$86.84	4.126%	$90.423	$90.42	$90.40	$90.40
Purchase #7	$49.49	8.407%	$53.6506	$53.65	$53.65	$53.70
7 purchase totals =	$884.53		$951.1580	$951.16	$951.15	$951.20