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	$51.60	7.525%	$55.4829	$55.48	$55.50	$55.50
Purchase #2	$150.66	4.856%	$157.976	$157.98	$158.00	$158.00
Purchase #3	$47.61	8.555%	$51.683	$51.68	$51.70	$51.70
Purchase #4	$217.39	8.190%	$235.1942	$235.19	$235.20	$235.20
Purchase #5	$247.43	3.258%	$255.4913	$255.49	$255.50	$255.50
Purchase #6	$77.69	10.543%	$85.8809	$85.88	$85.90	$85.90
Purchase #7	$235.62	8.418%	$255.4545	$255.45	$255.45	$255.50
7 purchase totals =	$1,028.00		$1,097.1628	$1,097.15	$1,097.25	$1,097.30