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	$234.25	9.205%	$255.8127	$255.81	$255.80	$255.80
Purchase #2	$142.48	6.401%	$151.6001	$151.60	$151.60	$151.60
Purchase #3	$115.52	9.827%	$126.8722	$126.87	$126.85	$126.90
Purchase #4	$157.62	6.427%	$167.7502	$167.75	$167.75	$167.80
Purchase #5	$95.62	4.815%	$100.2241	$100.22	$100.20	$100.20
Purchase #6	$47.63	5.337%	$50.172	$50.17	$50.15	$50.20
Purchase #7	$208.86	13.105%	$236.2311	$236.23	$236.25	$236.20
7 purchase totals =	$1,001.98		$1,088.6624	$1,088.65	$1,088.60	$1,088.70