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	$103.69	7.110%	$111.0624	$111.06	$111.05	$111.10
Purchase #2	$154.52	5.439%	$162.9243	$162.92	$162.90	$162.90
Purchase #3	$74.36	10.132%	$81.8942	$81.89	$81.90	$81.90
Purchase #4	$48.36	11.176%	$53.7647	$53.76	$53.75	$53.80
Purchase #5	$136.35	9.140%	$148.8124	$148.81	$148.80	$148.80
Purchase #6	$211.46	10.506%	$233.676	$233.68	$233.70	$233.70
Purchase #7	$143.97	7.848%	$155.2688	$155.27	$155.25	$155.30
7 purchase totals =	$872.71		$947.4028	$947.39	$947.35	$947.50