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	$162.36	10.563%	$179.5101	$179.51	$179.50	$179.50
Purchase #2	$77.99	12.358%	$87.628	$87.63	$87.65	$87.60
Purchase #3	$137.93	11.803%	$154.2099	$154.21	$154.20	$154.20
Purchase #4	$100.63	11.221%	$111.9217	$111.92	$111.90	$111.90
Purchase #5	$126.60	12.389%	$142.2845	$142.28	$142.30	$142.30
Purchase #6	$131.42	10.668%	$145.4399	$145.44	$145.45	$145.40
Purchase #7	$62.98	5.739%	$66.5944	$66.59	$66.60	$66.60
7 purchase totals =	$799.91		$887.5885	$887.58	$887.60	$887.50