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	$247.98	13.144%	$280.5745	$280.57	$280.55	$280.60
Purchase #2	$165.40	4.849%	$173.4202	$173.42	$173.40	$173.40
Purchase #3	$66.32	9.615%	$72.6967	$72.70	$72.70	$72.70
Purchase #4	$105.50	6.244%	$112.0874	$112.09	$112.10	$112.10
Purchase #5	$95.94	12.138%	$107.5852	$107.59	$107.60	$107.60
Purchase #6	$139.74	7.389%	$150.0654	$150.07	$150.05	$150.10
Purchase #7	$143.65	13.389%	$162.8833	$162.88	$162.90	$162.90
7 purchase totals =	$964.53		$1,059.3127	$1,059.32	$1,059.30	$1,059.40