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	$241.38	10.301%	$266.2446	$266.24	$266.25	$266.20
Purchase #2	$46.89	8.586%	$50.916	$50.92	$50.90	$50.90
Purchase #3	$103.35	8.143%	$111.7658	$111.77	$111.75	$111.80
Purchase #4	$48.51	9.510%	$53.1233	$53.12	$53.10	$53.10
Purchase #5	$138.75	11.376%	$154.5342	$154.53	$154.55	$154.50
Purchase #6	$12.36	13.364%	$14.0118	$14.01	$14.00	$14.00
Purchase #7	$102.99	8.672%	$111.9213	$111.92	$111.90	$111.90
7 purchase totals =	$694.23		$762.5170	$762.51	$762.45	$762.40