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	$158.83	13.683%	$180.5627	$180.56	$180.55	$180.60
Purchase #2	$96.29	4.421%	$100.547	$100.55	$100.55	$100.50
Purchase #3	$13.42	10.531%	$14.8333	$14.83	$14.85	$14.80
Purchase #4	$129.89	9.658%	$142.4348	$142.43	$142.45	$142.40
Purchase #5	$97.52	11.241%	$108.4822	$108.48	$108.50	$108.50
Purchase #6	$239.61	7.318%	$257.1447	$257.14	$257.15	$257.10
Purchase #7	$235.54	10.617%	$260.5473	$260.55	$260.55	$260.50
7 purchase totals =	$971.10		$1,064.5520	$1,064.54	$1,064.60	$1,064.40