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	$103.40	8.868%	$112.5695	$112.57	$112.55	$112.60
Purchase #2	$31.28	4.275%	$32.6172	$32.62	$32.60	$32.60
Purchase #3	$19.79	7.688%	$21.3115	$21.31	$21.30	$21.30
Purchase #4	$20.89	13.261%	$23.6602	$23.66	$23.65	$23.70
Purchase #5	$175.47	5.805%	$185.656	$185.66	$185.65	$185.70
Purchase #6	$190.27	10.320%	$209.9059	$209.91	$209.90	$209.90
Purchase #7	$15.96	3.370%	$16.4979	$16.50	$16.50	$16.50
7 purchase totals =	$557.06		$602.2182	$602.23	$602.15	$602.30