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	$239.37	10.225%	$263.8456	$263.85	$263.85	$263.80
Purchase #2	$46.70	3.397%	$48.2864	$48.29	$48.30	$48.30
Purchase #3	$246.40	4.278%	$256.941	$256.94	$256.95	$256.90
Purchase #4	$130.59	8.843%	$142.1381	$142.14	$142.15	$142.10
Purchase #5	$138.67	8.495%	$150.45	$150.45	$150.45	$150.50
Purchase #6	$233.42	12.633%	$262.9079	$262.91	$262.90	$262.90
Purchase #7	$47.37	10.679%	$52.4286	$52.43	$52.45	$52.40
7 purchase totals =	$1,082.52		$1,176.9976	$1,177.01	$1,177.05	$1,176.90