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	$237.47	7.334%	$254.886	$254.89	$254.90	$254.90
Purchase #2	$109.25	12.758%	$123.1881	$123.19	$123.20	$123.20
Purchase #3	$173.78	5.594%	$183.5013	$183.50	$183.50	$183.50
Purchase #4	$150.88	9.809%	$165.6798	$165.68	$165.70	$165.70
Purchase #5	$144.52	7.656%	$155.5845	$155.58	$155.60	$155.60
Purchase #6	$138.39	13.367%	$156.8886	$156.89	$156.90	$156.90
Purchase #7	$32.53	6.853%	$34.7593	$34.76	$34.75	$34.80
7 purchase totals =	$986.82		$1,074.4876	$1,074.49	$1,074.55	$1,074.60