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	$186.45	6.806%	$199.1398	$199.14	$199.15	$199.10
Purchase #2	$195.62	6.434%	$208.2062	$208.21	$208.20	$208.20
Purchase #3	$17.50	4.381%	$18.2667	$18.27	$18.25	$18.30
Purchase #4	$204.86	9.708%	$224.7478	$224.75	$224.75	$224.70
Purchase #5	$250.53	7.210%	$268.5932	$268.59	$268.60	$268.60
Purchase #6	$141.42	7.145%	$151.5245	$151.52	$151.50	$151.50
Purchase #7	$216.72	6.155%	$230.0591	$230.06	$230.05	$230.10
7 purchase totals =	$1,213.10		$1,300.5373	$1,300.54	$1,300.50	$1,300.50