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	$154.85	11.269%	$172.3	$172.30	$172.30	$172.30
Purchase #2	$41.96	11.362%	$46.7275	$46.73	$46.75	$46.70
Purchase #3	$123.40	4.250%	$128.6445	$128.64	$128.65	$128.60
Purchase #4	$104.31	8.209%	$112.8728	$112.87	$112.85	$112.90
Purchase #5	$217.75	10.195%	$239.9496	$239.95	$239.95	$239.90
Purchase #6	$130.89	7.852%	$141.1675	$141.17	$141.15	$141.20
Purchase #7	$94.85	11.462%	$105.7217	$105.72	$105.70	$105.70
7 purchase totals =	$868.01		$947.3836	$947.38	$947.35	$947.30