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	$12.27	7.767%	$13.223	$13.22	$13.20	$13.20
Purchase #2	$74.91	13.493%	$85.0176	$85.02	$85.00	$85.00
Purchase #3	$176.35	4.648%	$184.5467	$184.55	$184.55	$184.50
Purchase #4	$97.57	13.851%	$111.0844	$111.08	$111.10	$111.10
Purchase #5	$92.75	11.655%	$103.56	$103.56	$103.55	$103.60
Purchase #6	$50.53	4.107%	$52.6053	$52.61	$52.60	$52.60
Purchase #7	$168.43	3.492%	$174.3116	$174.31	$174.30	$174.30
7 purchase totals =	$672.81		$724.3486	$724.35	$724.30	$724.30