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	$200.34	10.147%	$220.6685	$220.67	$220.65	$220.70
Purchase #2	$227.46	12.380%	$255.6195	$255.62	$255.60	$255.60
Purchase #3	$107.71	11.560%	$120.1613	$120.16	$120.15	$120.20
Purchase #4	$176.80	7.619%	$190.2704	$190.27	$190.25	$190.30
Purchase #5	$52.43	4.160%	$54.6111	$54.61	$54.60	$54.60
Purchase #6	$136.61	12.103%	$153.1439	$153.14	$153.15	$153.10
Purchase #7	$19.80	9.320%	$21.6454	$21.65	$21.65	$21.60
7 purchase totals =	$921.15		$1,016.1201	$1,016.12	$1,016.05	$1,016.10