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	$163.42	13.422%	$185.3542	$185.35	$185.35	$185.40
Purchase #2	$48.36	9.317%	$52.8657	$52.87	$52.85	$52.90
Purchase #3	$95.25	11.151%	$105.8713	$105.87	$105.85	$105.90
Purchase #4	$161.93	7.220%	$173.6213	$173.62	$173.60	$173.60
Purchase #5	$85.50	10.515%	$94.4903	$94.49	$94.50	$94.50
Purchase #6	$164.88	11.538%	$183.9039	$183.90	$183.90	$183.90
Purchase #7	$128.64	13.664%	$146.2174	$146.22	$146.20	$146.20
7 purchase totals =	$847.98		$942.3241	$942.32	$942.25	$942.40