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	$216.47	6.491%	$230.5211	$230.52	$230.50	$230.50
Purchase #2	$218.61	10.263%	$241.0459	$241.05	$241.05	$241.00
Purchase #3	$163.72	9.771%	$179.7171	$179.72	$179.70	$179.70
Purchase #4	$242.29	6.431%	$257.8717	$257.87	$257.85	$257.90
Purchase #5	$63.57	5.391%	$66.9971	$67.00	$67.00	$67.00
Purchase #6	$40.88	6.701%	$43.6194	$43.62	$43.60	$43.60
Purchase #7	$166.26	6.137%	$176.4634	$176.46	$176.45	$176.50
7 purchase totals =	$1,111.80		$1,196.2357	$1,196.24	$1,196.15	$1,196.20