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	$203.85	6.852%	$217.8178	$217.82	$217.80	$217.80
Purchase #2	$120.87	5.487%	$127.5021	$127.50	$127.50	$127.50
Purchase #3	$10.55	11.614%	$11.7753	$11.78	$11.80	$11.80
Purchase #4	$143.82	5.409%	$151.5992	$151.60	$151.60	$151.60
Purchase #5	$129.80	10.236%	$143.0863	$143.09	$143.10	$143.10
Purchase #6	$186.42	3.386%	$192.7322	$192.73	$192.75	$192.70
Purchase #7	$147.27	7.280%	$157.9913	$157.99	$158.00	$158.00
7 purchase totals =	$942.58		$1,002.5042	$1,002.51	$1,002.55	$1,002.50