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	$62.68	12.283%	$70.379	$70.38	$70.40	$70.40
Purchase #2	$100.59	4.307%	$104.9224	$104.92	$104.90	$104.90
Purchase #3	$224.75	13.632%	$255.3879	$255.39	$255.40	$255.40
Purchase #4	$111.68	4.750%	$116.9848	$116.98	$117.00	$117.00
Purchase #5	$74.60	4.825%	$78.1995	$78.20	$78.20	$78.20
Purchase #6	$172.64	8.565%	$187.4266	$187.43	$187.45	$187.40
Purchase #7	$229.54	7.439%	$246.6155	$246.62	$246.60	$246.60
7 purchase totals =	$976.48		$1,059.9157	$1,059.92	$1,059.95	$1,059.90