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	$12.35	10.235%	$13.614	$13.61	$13.60	$13.60
Purchase #2	$219.40	13.612%	$249.2647	$249.26	$249.25	$249.30
Purchase #3	$122.93	7.695%	$132.3895	$132.39	$132.40	$132.40
Purchase #4	$241.49	11.764%	$269.8989	$269.90	$269.90	$269.90
Purchase #5	$93.59	5.872%	$99.0856	$99.09	$99.10	$99.10
Purchase #6	$128.88	10.824%	$142.83	$142.83	$142.85	$142.80
Purchase #7	$116.83	8.315%	$126.5444	$126.54	$126.55	$126.50
7 purchase totals =	$935.47		$1,033.6271	$1,033.62	$1,033.65	$1,033.60