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	$182.69	12.460%	$205.4532	$205.45	$205.45	$205.50
Purchase #2	$58.91	11.201%	$65.5085	$65.51	$65.50	$65.50
Purchase #3	$217.87	7.178%	$233.5087	$233.51	$233.50	$233.50
Purchase #4	$226.67	13.166%	$256.5134	$256.51	$256.50	$256.50
Purchase #5	$47.38	12.600%	$53.3499	$53.35	$53.35	$53.30
Purchase #6	$159.79	7.525%	$171.8142	$171.81	$171.80	$171.80
Purchase #7	$158.62	8.468%	$172.0519	$172.05	$172.05	$172.10
7 purchase totals =	$1,051.93		$1,158.1998	$1,158.19	$1,158.15	$1,158.20