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	$94.63	9.466%	$103.5877	$103.59	$103.60	$103.60
Purchase #2	$59.29	13.675%	$67.3979	$67.40	$67.40	$67.40
Purchase #3	$241.96	8.298%	$262.0378	$262.04	$262.05	$262.00
Purchase #4	$204.61	13.350%	$231.9254	$231.93	$231.95	$231.90
Purchase #5	$235.79	13.169%	$266.8412	$266.84	$266.85	$266.80
Purchase #6	$121.80	13.165%	$137.835	$137.84	$137.85	$137.80
Purchase #7	$98.42	4.668%	$103.0142	$103.01	$103.00	$103.00
7 purchase totals =	$1,056.50		$1,172.6392	$1,172.65	$1,172.70	$1,172.50