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	$100.26	8.811%	$109.0939	$109.09	$109.10	$109.10
Purchase #2	$83.50	13.200%	$94.522	$94.52	$94.50	$94.50
Purchase #3	$8.28	4.297%	$8.6358	$8.64	$8.65	$8.60
Purchase #4	$127.79	3.670%	$132.4799	$132.48	$132.50	$132.50
Purchase #5	$142.75	9.169%	$155.8387	$155.84	$155.85	$155.80
Purchase #6	$201.58	10.162%	$222.0646	$222.06	$222.05	$222.10
Purchase #7	$31.43	6.328%	$33.4189	$33.42	$33.40	$33.40
7 purchase totals =	$695.59		$756.0538	$756.05	$756.05	$756.00