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	$86.59	4.332%	$90.3411	$90.34	$90.35	$90.30
Purchase #2	$51.89	4.824%	$54.3932	$54.39	$54.40	$54.40
Purchase #3	$188.38	5.770%	$199.2495	$199.25	$199.25	$199.20
Purchase #4	$153.42	3.393%	$158.6255	$158.63	$158.65	$158.60
Purchase #5	$89.52	9.412%	$97.9456	$97.95	$97.95	$97.90
Purchase #6	$111.83	11.506%	$124.6972	$124.70	$124.70	$124.70
Purchase #7	$11.39	12.504%	$12.8142	$12.81	$12.80	$12.80
7 purchase totals =	$693.02		$738.0663	$738.07	$738.10	$737.90