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	$216.27	3.754%	$224.3888	$224.39	$224.40	$224.40
Purchase #2	$204.86	5.188%	$215.4881	$215.49	$215.50	$215.50
Purchase #3	$9.41	6.361%	$10.0086	$10.01	$10.00	$10.00
Purchase #4	$70.31	5.104%	$73.8986	$73.90	$73.90	$73.90
Purchase #5	$204.50	12.684%	$230.4388	$230.44	$230.45	$230.40
Purchase #6	$11.56	11.760%	$12.9195	$12.92	$12.90	$12.90
Purchase #7	$235.72	7.481%	$253.3542	$253.35	$253.35	$253.40
7 purchase totals =	$952.63		$1,020.4966	$1,020.50	$1,020.50	$1,020.50