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	$235.44	3.164%	$242.8893	$242.89	$242.90	$242.90
Purchase #2	$5.44	8.827%	$5.9202	$5.92	$5.90	$5.90
Purchase #3	$130.39	12.338%	$146.4775	$146.48	$146.50	$146.50
Purchase #4	$159.54	12.313%	$179.1842	$179.18	$179.20	$179.20
Purchase #5	$13.41	5.470%	$14.1435	$14.14	$14.15	$14.10
Purchase #6	$32.97	12.496%	$37.0899	$37.09	$37.10	$37.10
Purchase #7	$103.62	7.747%	$111.6474	$111.65	$111.65	$111.60
7 purchase totals =	$680.81		$737.3520	$737.35	$737.40	$737.30