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	$123.72	3.483%	$128.0292	$128.03	$128.05	$128.00
Purchase #2	$11.46	11.777%	$12.8096	$12.81	$12.80	$12.80
Purchase #3	$241.29	5.749%	$255.1618	$255.16	$255.15	$255.20
Purchase #4	$149.62	5.411%	$157.7159	$157.72	$157.70	$157.70
Purchase #5	$201.76	10.403%	$222.7491	$222.75	$222.75	$222.70
Purchase #6	$120.90	5.799%	$127.911	$127.91	$127.90	$127.90
Purchase #7	$57.28	8.712%	$62.2702	$62.27	$62.25	$62.30
7 purchase totals =	$906.03		$966.6468	$966.65	$966.60	$966.60