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	$32.60	10.554%	$36.0406	$36.04	$36.05	$36.00
Purchase #2	$121.54	4.734%	$127.2937	$127.29	$127.30	$127.30
Purchase #3	$232.31	7.834%	$250.5092	$250.51	$250.50	$250.50
Purchase #4	$11.83	8.413%	$12.8253	$12.83	$12.85	$12.80
Purchase #5	$13.34	3.243%	$13.7726	$13.77	$13.75	$13.80
Purchase #6	$132.61	10.485%	$146.5142	$146.51	$146.50	$146.50
Purchase #7	$134.45	8.370%	$145.7035	$145.70	$145.70	$145.70
7 purchase totals =	$678.68		$732.6591	$732.65	$732.65	$732.60