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	$220.53	4.545%	$230.5531	$230.55	$230.55	$230.60
Purchase #2	$137.79	10.671%	$152.4936	$152.49	$152.50	$152.50
Purchase #3	$105.37	12.262%	$118.2905	$118.29	$118.30	$118.30
Purchase #4	$97.84	13.745%	$111.2881	$111.29	$111.30	$111.30
Purchase #5	$248.26	8.818%	$270.1516	$270.15	$270.15	$270.20
Purchase #6	$76.44	9.650%	$83.8165	$83.82	$83.80	$83.80
Purchase #7	$90.62	10.673%	$100.2919	$100.29	$100.30	$100.30
7 purchase totals =	$976.85		$1,066.8853	$1,066.88	$1,066.90	$1,067.00