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	$87.26	10.483%	$96.4075	$96.41	$96.40	$96.40
Purchase #2	$14.98	4.103%	$15.5946	$15.59	$15.60	$15.60
Purchase #3	$76.69	12.443%	$86.2325	$86.23	$86.25	$86.20
Purchase #4	$168.75	13.676%	$191.8283	$191.83	$191.85	$191.80
Purchase #5	$20.52	3.168%	$21.1701	$21.17	$21.15	$21.20
Purchase #6	$47.74	5.751%	$50.4855	$50.49	$50.50	$50.50
Purchase #7	$64.62	3.190%	$66.6814	$66.68	$66.70	$66.70
7 purchase totals =	$480.56		$528.3999	$528.40	$528.45	$528.40