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	$96.38	13.734%	$109.6168	$109.62	$109.60	$109.60
Purchase #2	$152.60	10.433%	$168.5208	$168.52	$168.50	$168.50
Purchase #3	$200.52	7.456%	$215.4708	$215.47	$215.45	$215.50
Purchase #4	$45.95	4.613%	$48.0697	$48.07	$48.05	$48.10
Purchase #5	$237.66	9.753%	$260.839	$260.84	$260.85	$260.80
Purchase #6	$218.68	3.161%	$225.5925	$225.59	$225.60	$225.60
Purchase #7	$98.28	4.383%	$102.5876	$102.59	$102.60	$102.60
7 purchase totals =	$1,050.07		$1,130.6972	$1,130.70	$1,130.65	$1,130.70