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	$141.66	8.255%	$153.354	$153.35	$153.35	$153.40
Purchase #2	$139.37	13.244%	$157.8282	$157.83	$157.85	$157.80
Purchase #3	$42.77	8.658%	$46.473	$46.47	$46.45	$46.50
Purchase #4	$50.38	11.402%	$56.1243	$56.12	$56.10	$56.10
Purchase #5	$72.35	12.538%	$81.4212	$81.42	$81.40	$81.40
Purchase #6	$80.69	10.784%	$89.3916	$89.39	$89.40	$89.40
Purchase #7	$153.60	11.854%	$171.8077	$171.81	$171.80	$171.80
7 purchase totals =	$680.82		$756.4000	$756.39	$756.35	$756.40