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	$248.72	7.289%	$266.8492	$266.85	$266.85	$266.80
Purchase #2	$75.83	8.132%	$81.9965	$82.00	$82.00	$82.00
Purchase #3	$248.72	11.851%	$278.1958	$278.20	$278.20	$278.20
Purchase #4	$144.85	8.493%	$157.1521	$157.15	$157.15	$157.20
Purchase #5	$196.32	12.399%	$220.6617	$220.66	$220.65	$220.70
Purchase #6	$120.34	5.806%	$127.3269	$127.33	$127.35	$127.30
Purchase #7	$100.72	10.518%	$111.3137	$111.31	$111.30	$111.30
7 purchase totals =	$1,135.50		$1,243.4959	$1,243.50	$1,243.50	$1,243.50