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	$159.69	10.611%	$176.6347	$176.63	$176.65	$176.60
Purchase #2	$149.38	11.262%	$166.2032	$166.20	$166.20	$166.20
Purchase #3	$237.25	10.706%	$262.65	$262.65	$262.65	$262.70
Purchase #4	$74.42	11.388%	$82.8949	$82.89	$82.90	$82.90
Purchase #5	$247.61	13.794%	$281.7653	$281.77	$281.75	$281.80
Purchase #6	$70.72	10.748%	$78.321	$78.32	$78.30	$78.30
Purchase #7	$68.93	5.325%	$72.6005	$72.60	$72.60	$72.60
7 purchase totals =	$1,008.00		$1,121.0696	$1,121.06	$1,121.05	$1,121.10