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	$99.97	11.109%	$111.0757	$111.08	$111.10	$111.10
Purchase #2	$224.72	11.186%	$249.8572	$249.86	$249.85	$249.90
Purchase #3	$169.68	13.177%	$192.0387	$192.04	$192.05	$192.00
Purchase #4	$214.78	4.698%	$224.8704	$224.87	$224.85	$224.90
Purchase #5	$179.87	5.704%	$190.1298	$190.13	$190.15	$190.10
Purchase #6	$95.62	8.662%	$103.9026	$103.90	$103.90	$103.90
Purchase #7	$108.39	5.118%	$113.9374	$113.94	$113.95	$113.90
7 purchase totals =	$1,093.03		$1,185.8118	$1,185.82	$1,185.85	$1,185.80