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	$71.72	9.323%	$78.4065	$78.41	$78.40	$78.40
Purchase #2	$108.40	3.298%	$111.975	$111.98	$112.00	$112.00
Purchase #3	$115.77	9.373%	$126.6211	$126.62	$126.60	$126.60
Purchase #4	$17.50	4.654%	$18.3145	$18.31	$18.30	$18.30
Purchase #5	$212.94	7.452%	$228.8083	$228.81	$228.80	$228.80
Purchase #6	$14.39	10.414%	$15.8886	$15.89	$15.90	$15.90
Purchase #7	$51.94	3.274%	$53.6405	$53.64	$53.65	$53.60
7 purchase totals =	$592.66		$633.6545	$633.66	$633.65	$633.60