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	$40.75	10.292%	$44.944	$44.94	$44.95	$44.90
Purchase #2	$116.36	6.370%	$123.7721	$123.77	$123.75	$123.80
Purchase #3	$50.38	5.526%	$53.164	$53.16	$53.15	$53.20
Purchase #4	$62.26	7.656%	$67.0266	$67.03	$67.05	$67.00
Purchase #5	$60.78	11.870%	$67.9946	$67.99	$68.00	$68.00
Purchase #6	$116.29	6.382%	$123.7116	$123.71	$123.70	$123.70
Purchase #7	$141.79	11.733%	$158.4262	$158.43	$158.45	$158.40
7 purchase totals =	$588.61		$639.0391	$639.03	$639.05	$639.00