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	$53.46	6.337%	$56.8478	$56.85	$56.85	$56.80
Purchase #2	$33.96	3.120%	$35.0196	$35.02	$35.00	$35.00
Purchase #3	$194.60	5.388%	$205.085	$205.09	$205.10	$205.10
Purchase #4	$221.43	9.337%	$242.1049	$242.10	$242.10	$242.10
Purchase #5	$151.70	10.405%	$167.4844	$167.48	$167.50	$167.50
Purchase #6	$80.38	12.453%	$90.3897	$90.39	$90.40	$90.40
Purchase #7	$244.66	11.280%	$272.2576	$272.26	$272.25	$272.30
7 purchase totals =	$980.19		$1,069.1890	$1,069.19	$1,069.20	$1,069.20