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	$97.93	13.787%	$111.4316	$111.43	$111.45	$111.40
Purchase #2	$50.84	10.457%	$56.1563	$56.16	$56.15	$56.20
Purchase #3	$10.45	3.275%	$10.7922	$10.79	$10.80	$10.80
Purchase #4	$40.28	5.823%	$42.6255	$42.63	$42.65	$42.60
Purchase #5	$63.91	6.426%	$68.0169	$68.02	$68.00	$68.00
Purchase #6	$188.30	9.146%	$205.5219	$205.52	$205.50	$205.50
Purchase #7	$22.80	4.756%	$23.8844	$23.88	$23.90	$23.90
7 purchase totals =	$474.51		$518.4288	$518.43	$518.45	$518.40