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	$104.39	6.456%	$111.1294	$111.13	$111.15	$111.10
Purchase #2	$126.57	4.600%	$132.3922	$132.39	$132.40	$132.40
Purchase #3	$11.98	13.164%	$13.557	$13.56	$13.55	$13.60
Purchase #4	$247.87	4.111%	$258.0599	$258.06	$258.05	$258.10
Purchase #5	$40.72	10.657%	$45.0595	$45.06	$45.05	$45.10
Purchase #6	$148.58	3.798%	$154.2231	$154.22	$154.20	$154.20
Purchase #7	$5.40	12.423%	$6.0708	$6.07	$6.05	$6.10
7 purchase totals =	$685.51		$720.4919	$720.49	$720.45	$720.60