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	$198.56	9.367%	$217.1591	$217.16	$217.15	$217.20
Purchase #2	$157.75	13.571%	$179.1583	$179.16	$179.15	$179.20
Purchase #3	$111.97	8.616%	$121.6173	$121.62	$121.60	$121.60
Purchase #4	$100.79	10.745%	$111.6199	$111.62	$111.60	$111.60
Purchase #5	$149.63	5.826%	$158.3474	$158.35	$158.35	$158.30
Purchase #6	$176.46	6.138%	$187.2911	$187.29	$187.30	$187.30
Purchase #7	$142.30	7.385%	$152.8089	$152.81	$152.80	$152.80
7 purchase totals =	$1,037.46		$1,128.0020	$1,128.01	$1,127.95	$1,128.00