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	$164.30	11.724%	$183.5625	$183.56	$183.55	$183.60
Purchase #2	$212.67	10.286%	$234.5452	$234.55	$234.55	$234.50
Purchase #3	$221.68	7.501%	$238.3082	$238.31	$238.30	$238.30
Purchase #4	$116.61	6.180%	$123.8165	$123.82	$123.80	$123.80
Purchase #5	$143.28	3.440%	$148.2088	$148.21	$148.20	$148.20
Purchase #6	$138.28	10.827%	$153.2516	$153.25	$153.25	$153.30
Purchase #7	$199.59	8.699%	$216.9523	$216.95	$216.95	$217.00
7 purchase totals =	$1,196.41		$1,298.6451	$1,298.65	$1,298.60	$1,298.70