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	$164.54	8.537%	$178.5868	$178.59	$178.60	$178.60
Purchase #2	$105.67	5.810%	$111.8094	$111.81	$111.80	$111.80
Purchase #3	$102.70	12.417%	$115.4523	$115.45	$115.45	$115.50
Purchase #4	$205.44	5.110%	$215.938	$215.94	$215.95	$215.90
Purchase #5	$221.66	10.281%	$244.4489	$244.45	$244.45	$244.40
Purchase #6	$6.56	9.189%	$7.1628	$7.16	$7.15	$7.20
Purchase #7	$226.90	5.540%	$239.4703	$239.47	$239.45	$239.50
7 purchase totals =	$1,033.47		$1,112.8685	$1,112.87	$1,112.85	$1,112.90