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	$48.60	8.537%	$52.749	$52.75	$52.75	$52.70
Purchase #2	$202.91	6.194%	$215.4782	$215.48	$215.50	$215.50
Purchase #3	$114.55	11.256%	$127.4437	$127.44	$127.45	$127.40
Purchase #4	$62.84	13.538%	$71.3473	$71.35	$71.35	$71.30
Purchase #5	$104.44	8.499%	$113.3164	$113.32	$113.30	$113.30
Purchase #6	$126.29	3.739%	$131.012	$131.01	$131.00	$131.00
Purchase #7	$138.89	10.472%	$153.4346	$153.43	$153.45	$153.40
7 purchase totals =	$798.52		$864.7812	$864.78	$864.80	$864.60