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	$130.72	10.211%	$144.0678	$144.07	$144.05	$144.10
Purchase #2	$182.62	7.602%	$196.5028	$196.50	$196.50	$196.50
Purchase #3	$146.50	13.237%	$165.8922	$165.89	$165.90	$165.90
Purchase #4	$217.27	5.491%	$229.2003	$229.20	$229.20	$229.20
Purchase #5	$117.35	9.108%	$128.0382	$128.04	$128.05	$128.00
Purchase #6	$132.81	7.212%	$142.3883	$142.39	$142.40	$142.40
Purchase #7	$243.77	6.129%	$258.7107	$258.71	$258.70	$258.70
7 purchase totals =	$1,171.04		$1,264.8003	$1,264.80	$1,264.80	$1,264.80