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	$163.45	5.392%	$172.2632	$172.26	$172.25	$172.30
Purchase #2	$220.71	4.410%	$230.4433	$230.44	$230.45	$230.40
Purchase #3	$164.30	3.514%	$170.0735	$170.07	$170.05	$170.10
Purchase #4	$181.25	5.123%	$190.5354	$190.54	$190.55	$190.50
Purchase #5	$218.69	5.384%	$230.4643	$230.46	$230.45	$230.50
Purchase #6	$248.54	12.212%	$278.8917	$278.89	$278.90	$278.90
Purchase #7	$10.29	11.745%	$11.4986	$11.50	$11.50	$11.50
7 purchase totals =	$1,207.23		$1,284.1700	$1,284.16	$1,284.15	$1,284.20