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	$79.46	5.524%	$83.8494	$83.85	$83.85	$83.80
Purchase #2	$184.96	4.245%	$192.8116	$192.81	$192.80	$192.80
Purchase #3	$233.44	3.800%	$242.3107	$242.31	$242.30	$242.30
Purchase #4	$118.56	7.486%	$127.4354	$127.44	$127.45	$127.40
Purchase #5	$204.40	9.506%	$223.8303	$223.83	$223.85	$223.80
Purchase #6	$156.65	10.772%	$173.5243	$173.52	$173.50	$173.50
Purchase #7	$11.41	6.136%	$12.1101	$12.11	$12.10	$12.10
7 purchase totals =	$988.88		$1,055.8718	$1,055.87	$1,055.85	$1,055.70