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	$40.77	6.458%	$43.4029	$43.40	$43.40	$43.40
Purchase #2	$68.64	8.752%	$74.6474	$74.65	$74.65	$74.60
Purchase #3	$106.42	7.810%	$114.7314	$114.73	$114.75	$114.70
Purchase #4	$52.58	12.232%	$59.0116	$59.01	$59.00	$59.00
Purchase #5	$205.86	3.153%	$212.3508	$212.35	$212.35	$212.40
Purchase #6	$83.50	7.336%	$89.6256	$89.63	$89.65	$89.60
Purchase #7	$139.30	8.845%	$151.6211	$151.62	$151.60	$151.60
7 purchase totals =	$697.07		$745.3908	$745.39	$745.40	$745.30