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	$245.66	8.589%	$266.7597	$266.76	$266.75	$266.80
Purchase #2	$88.72	13.388%	$100.5978	$100.60	$100.60	$100.60
Purchase #3	$180.97	6.265%	$192.3078	$192.31	$192.30	$192.30
Purchase #4	$37.65	10.684%	$41.6725	$41.67	$41.65	$41.70
Purchase #5	$219.89	3.336%	$227.2255	$227.23	$227.25	$227.20
Purchase #6	$112.53	13.443%	$127.6574	$127.66	$127.65	$127.70
Purchase #7	$56.84	11.688%	$63.4835	$63.48	$63.50	$63.50
7 purchase totals =	$942.26		$1,019.7042	$1,019.71	$1,019.70	$1,019.80