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	$40.99	7.355%	$44.0048	$44.00	$44.00	$44.00
Purchase #2	$78.78	6.233%	$83.6904	$83.69	$83.70	$83.70
Purchase #3	$29.88	11.387%	$33.2824	$33.28	$33.30	$33.30
Purchase #4	$81.51	10.359%	$89.9536	$89.95	$89.95	$90.00
Purchase #5	$49.85	12.857%	$56.2592	$56.26	$56.25	$56.30
Purchase #6	$39.97	11.654%	$44.6281	$44.63	$44.65	$44.60
Purchase #7	$59.46	5.322%	$62.6245	$62.62	$62.60	$62.60
7 purchase totals =	$380.44		$414.4430	$414.43	$414.45	$414.50