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	$31.87	4.316%	$33.2455	$33.25	$33.25	$33.20
Purchase #2	$33.54	11.163%	$37.2841	$37.28	$37.30	$37.30
Purchase #3	$143.30	5.662%	$151.4136	$151.41	$151.40	$151.40
Purchase #4	$220.50	13.218%	$249.6457	$249.65	$249.65	$249.60
Purchase #5	$46.83	6.760%	$49.9957	$50.00	$50.00	$50.00
Purchase #6	$145.64	8.813%	$158.4753	$158.48	$158.50	$158.50
Purchase #7	$31.41	9.232%	$34.3098	$34.31	$34.30	$34.30
7 purchase totals =	$653.09		$714.3697	$714.38	$714.40	$714.30