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	$134.62	7.285%	$144.4271	$144.43	$144.45	$144.40
Purchase #2	$168.67	5.801%	$178.4545	$178.45	$178.45	$178.50
Purchase #3	$146.47	8.353%	$158.7046	$158.70	$158.70	$158.70
Purchase #4	$51.53	9.199%	$56.2702	$56.27	$56.25	$56.30
Purchase #5	$221.43	10.466%	$244.6049	$244.60	$244.60	$244.60
Purchase #6	$37.27	3.239%	$38.4772	$38.48	$38.50	$38.50
Purchase #7	$34.36	13.319%	$38.9364	$38.94	$38.95	$38.90
7 purchase totals =	$794.35		$859.8749	$859.87	$859.90	$859.90