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	$241.52	7.814%	$260.3924	$260.39	$260.40	$260.40
Purchase #2	$184.31	6.490%	$196.2717	$196.27	$196.25	$196.30
Purchase #3	$11.61	6.710%	$12.389	$12.39	$12.40	$12.40
Purchase #4	$70.39	13.832%	$80.1263	$80.13	$80.15	$80.10
Purchase #5	$34.75	13.701%	$39.5111	$39.51	$39.50	$39.50
Purchase #6	$228.67	11.769%	$255.5822	$255.58	$255.60	$255.60
Purchase #7	$84.25	6.126%	$89.4112	$89.41	$89.40	$89.40
7 purchase totals =	$855.50		$933.6839	$933.68	$933.70	$933.70