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	$119.52	9.724%	$131.1421	$131.14	$131.15	$131.10
Purchase #2	$161.61	10.866%	$179.1705	$179.17	$179.15	$179.20
Purchase #3	$32.43	5.198%	$34.1157	$34.12	$34.10	$34.10
Purchase #4	$118.43	5.422%	$124.8513	$124.85	$124.85	$124.90
Purchase #5	$122.55	4.215%	$127.7155	$127.72	$127.70	$127.70
Purchase #6	$119.68	13.834%	$136.2365	$136.24	$136.25	$136.20
Purchase #7	$42.26	9.439%	$46.2489	$46.25	$46.25	$46.20
7 purchase totals =	$716.48		$779.4805	$779.49	$779.45	$779.40