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	$35.31	4.829%	$37.0151	$37.02	$37.00	$37.00
Purchase #2	$214.57	8.866%	$233.5938	$233.59	$233.60	$233.60
Purchase #3	$242.53	3.738%	$251.5958	$251.60	$251.60	$251.60
Purchase #4	$151.66	13.613%	$172.3055	$172.31	$172.30	$172.30
Purchase #5	$137.91	4.224%	$143.7353	$143.74	$143.75	$143.70
Purchase #6	$170.98	11.452%	$190.5606	$190.56	$190.55	$190.60
Purchase #7	$176.68	9.843%	$194.0706	$194.07	$194.05	$194.10
7 purchase totals =	$1,129.64		$1,222.8767	$1,222.89	$1,222.85	$1,222.90