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	$138.72	11.855%	$155.1653	$155.17	$155.15	$155.20
Purchase #2	$114.65	11.354%	$127.6674	$127.67	$127.65	$127.70
Purchase #3	$239.25	8.851%	$260.426	$260.43	$260.45	$260.40
Purchase #4	$157.92	10.346%	$174.2584	$174.26	$174.25	$174.30
Purchase #5	$208.46	12.221%	$233.9359	$233.94	$233.95	$233.90
Purchase #6	$13.99	4.632%	$14.638	$14.64	$14.65	$14.60
Purchase #7	$86.46	3.371%	$89.3746	$89.37	$89.35	$89.40
7 purchase totals =	$959.45		$1,055.4656	$1,055.48	$1,055.45	$1,055.50