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	$84.74	8.720%	$92.1293	$92.13	$92.15	$92.10
Purchase #2	$45.50	6.756%	$48.574	$48.57	$48.55	$48.60
Purchase #3	$158.42	11.619%	$176.8268	$176.83	$176.85	$176.80
Purchase #4	$237.92	7.549%	$255.8806	$255.88	$255.90	$255.90
Purchase #5	$60.57	7.323%	$65.0055	$65.01	$65.00	$65.00
Purchase #6	$158.41	7.660%	$170.5442	$170.54	$170.55	$170.50
Purchase #7	$216.45	9.736%	$237.5236	$237.52	$237.50	$237.50
7 purchase totals =	$962.01		$1,046.4840	$1,046.48	$1,046.50	$1,046.40