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	$158.27	9.203%	$172.8356	$172.84	$172.85	$172.80
Purchase #2	$13.59	13.605%	$15.4389	$15.44	$15.45	$15.40
Purchase #3	$100.93	13.865%	$114.9239	$114.92	$114.90	$114.90
Purchase #4	$144.74	12.712%	$163.1393	$163.14	$163.15	$163.10
Purchase #5	$99.60	11.483%	$111.0371	$111.04	$111.05	$111.00
Purchase #6	$204.79	12.656%	$230.7082	$230.71	$230.70	$230.70
Purchase #7	$193.75	3.440%	$200.415	$200.42	$200.40	$200.40
7 purchase totals =	$915.67		$1,008.4980	$1,008.51	$1,008.50	$1,008.30