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	$231.58	9.761%	$254.1845	$254.18	$254.20	$254.20
Purchase #2	$123.63	7.627%	$133.0593	$133.06	$133.05	$133.10
Purchase #3	$19.53	5.411%	$20.5868	$20.59	$20.60	$20.60
Purchase #4	$148.52	10.201%	$163.6705	$163.67	$163.65	$163.70
Purchase #5	$96.60	7.250%	$103.6035	$103.60	$103.60	$103.60
Purchase #6	$72.81	8.123%	$78.7244	$78.72	$78.70	$78.70
Purchase #7	$226.80	12.249%	$254.5807	$254.58	$254.60	$254.60
7 purchase totals =	$919.47		$1,008.4097	$1,008.40	$1,008.40	$1,008.50