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	$229.28	11.414%	$255.45	$255.45	$255.45	$255.50
Purchase #2	$74.86	11.671%	$83.5969	$83.60	$83.60	$83.60
Purchase #3	$166.87	9.238%	$182.2855	$182.29	$182.30	$182.30
Purchase #4	$111.98	11.301%	$124.6349	$124.63	$124.65	$124.60
Purchase #5	$165.84	13.274%	$187.8536	$187.85	$187.85	$187.90
Purchase #6	$148.55	6.644%	$158.4197	$158.42	$158.40	$158.40
Purchase #7	$243.37	4.140%	$253.4455	$253.45	$253.45	$253.40
7 purchase totals =	$1,140.75		$1,245.6861	$1,245.69	$1,245.70	$1,245.70