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	$241.71	5.521%	$255.0548	$255.05	$255.05	$255.10
Purchase #2	$195.53	9.422%	$213.9528	$213.95	$213.95	$214.00
Purchase #3	$225.47	11.463%	$251.3156	$251.32	$251.30	$251.30
Purchase #4	$158.66	9.466%	$173.6788	$173.68	$173.70	$173.70
Purchase #5	$229.32	13.653%	$260.6291	$260.63	$260.65	$260.60
Purchase #6	$110.59	11.642%	$123.4649	$123.46	$123.45	$123.50
Purchase #7	$35.32	5.347%	$37.2086	$37.21	$37.20	$37.20
7 purchase totals =	$1,196.60		$1,315.3046	$1,315.30	$1,315.30	$1,315.40