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	$245.75	4.234%	$256.1551	$256.16	$256.15	$256.20
Purchase #2	$121.74	4.393%	$127.088	$127.09	$127.10	$127.10
Purchase #3	$188.76	8.504%	$204.8122	$204.81	$204.80	$204.80
Purchase #4	$79.59	3.111%	$82.066	$82.07	$82.05	$82.10
Purchase #5	$229.49	6.698%	$244.8612	$244.86	$244.85	$244.90
Purchase #6	$16.27	13.632%	$18.4879	$18.49	$18.50	$18.50
Purchase #7	$173.86	13.131%	$196.6896	$196.69	$196.70	$196.70
7 purchase totals =	$1,055.46		$1,130.1600	$1,130.17	$1,130.15	$1,130.30