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	$179.46	11.212%	$199.5811	$199.58	$199.60	$199.60
Purchase #2	$157.31	10.346%	$173.5853	$173.59	$173.60	$173.60
Purchase #3	$72.45	11.727%	$80.9462	$80.95	$80.95	$80.90
Purchase #4	$69.63	6.854%	$74.4024	$74.40	$74.40	$74.40
Purchase #5	$185.66	12.482%	$208.8341	$208.83	$208.85	$208.80
Purchase #6	$107.40	3.724%	$111.3996	$111.40	$111.40	$111.40
Purchase #7	$94.83	5.545%	$100.0883	$100.09	$100.10	$100.10
7 purchase totals =	$866.74		$948.8370	$948.84	$948.90	$948.80