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	$146.70	12.599%	$165.1827	$165.18	$165.20	$165.20
Purchase #2	$248.64	9.145%	$271.3781	$271.38	$271.40	$271.40
Purchase #3	$201.35	3.235%	$207.8637	$207.86	$207.85	$207.90
Purchase #4	$50.73	3.786%	$52.6506	$52.65	$52.65	$52.70
Purchase #5	$128.37	12.361%	$144.2378	$144.24	$144.25	$144.20
Purchase #6	$92.52	8.527%	$100.4092	$100.41	$100.40	$100.40
Purchase #7	$152.50	13.277%	$172.7474	$172.75	$172.75	$172.70
7 purchase totals =	$1,020.81		$1,114.4695	$1,114.47	$1,114.50	$1,114.50