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	$184.42	6.626%	$196.6397	$196.64	$196.65	$196.60
Purchase #2	$116.25	5.448%	$122.5833	$122.58	$122.60	$122.60
Purchase #3	$241.49	5.606%	$255.0279	$255.03	$255.05	$255.00
Purchase #4	$123.57	13.241%	$139.9319	$139.93	$139.95	$139.90
Purchase #5	$149.87	6.779%	$160.0297	$160.03	$160.05	$160.00
Purchase #6	$94.38	11.391%	$105.1308	$105.13	$105.15	$105.10
Purchase #7	$180.89	13.757%	$205.775	$205.78	$205.80	$205.80
7 purchase totals =	$1,090.87		$1,185.1183	$1,185.12	$1,185.25	$1,185.00