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	$114.84	11.169%	$127.6665	$127.67	$127.65	$127.70
Purchase #2	$115.33	4.499%	$120.5187	$120.52	$120.50	$120.50
Purchase #3	$111.81	13.781%	$127.2185	$127.22	$127.20	$127.20
Purchase #4	$142.52	13.499%	$161.7588	$161.76	$161.75	$161.80
Purchase #5	$183.98	5.612%	$194.305	$194.31	$194.30	$194.30
Purchase #6	$34.30	3.486%	$35.4957	$35.50	$35.50	$35.50
Purchase #7	$135.50	5.603%	$143.0921	$143.09	$143.10	$143.10
7 purchase totals =	$838.28		$910.0553	$910.07	$910.00	$910.10