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	$89.31	11.536%	$99.6128	$99.61	$99.60	$99.60
Purchase #2	$114.88	7.645%	$123.6626	$123.66	$123.65	$123.70
Purchase #3	$22.72	4.633%	$23.7726	$23.77	$23.75	$23.80
Purchase #4	$48.26	6.235%	$51.269	$51.27	$51.25	$51.30
Purchase #5	$179.25	6.242%	$190.4388	$190.44	$190.45	$190.40
Purchase #6	$50.61	13.587%	$57.4864	$57.49	$57.50	$57.50
Purchase #7	$163.43	6.149%	$173.4793	$173.48	$173.50	$173.50
7 purchase totals =	$668.46		$719.7215	$719.72	$719.70	$719.80