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	$198.92	5.104%	$209.0729	$209.07	$209.05	$209.10
Purchase #2	$131.68	4.115%	$137.0986	$137.10	$137.10	$137.10
Purchase #3	$9.56	6.196%	$10.1523	$10.15	$10.15	$10.20
Purchase #4	$139.82	11.227%	$155.5176	$155.52	$155.50	$155.50
Purchase #5	$24.89	11.111%	$27.6555	$27.66	$27.65	$27.70
Purchase #6	$20.65	4.114%	$21.4995	$21.50	$21.50	$21.50
Purchase #7	$130.40	10.159%	$143.6473	$143.65	$143.65	$143.60
7 purchase totals =	$655.92		$704.6437	$704.65	$704.60	$704.70