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	$144.36	5.167%	$151.8191	$151.82	$151.80	$151.80
Purchase #2	$244.89	6.243%	$260.1785	$260.18	$260.20	$260.20
Purchase #3	$45.86	12.211%	$51.46	$51.46	$51.45	$51.50
Purchase #4	$117.38	13.225%	$132.9035	$132.90	$132.90	$132.90
Purchase #5	$91.58	9.430%	$100.216	$100.22	$100.20	$100.20
Purchase #6	$111.84	12.702%	$126.0459	$126.05	$126.05	$126.00
Purchase #7	$161.38	6.839%	$172.4168	$172.42	$172.40	$172.40
7 purchase totals =	$917.29		$995.0398	$995.05	$995.00	$995.00