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	$152.47	13.508%	$173.0656	$173.07	$173.05	$173.10
Purchase #2	$118.98	8.282%	$128.8339	$128.83	$128.85	$128.80
Purchase #3	$55.76	7.570%	$59.981	$59.98	$60.00	$60.00
Purchase #4	$83.75	5.664%	$88.4936	$88.49	$88.50	$88.50
Purchase #5	$42.94	12.443%	$48.283	$48.28	$48.30	$48.30
Purchase #6	$19.68	4.612%	$20.5876	$20.59	$20.60	$20.60
Purchase #7	$249.65	5.310%	$262.9064	$262.91	$262.90	$262.90
7 purchase totals =	$723.23		$782.1511	$782.15	$782.20	$782.20