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	$142.44	9.865%	$156.4917	$156.49	$156.50	$156.50
Purchase #2	$165.95	4.521%	$173.4526	$173.45	$173.45	$173.50
Purchase #3	$85.72	11.498%	$95.5761	$95.58	$95.60	$95.60
Purchase #4	$91.88	8.117%	$99.3379	$99.34	$99.35	$99.30
Purchase #5	$132.75	4.292%	$138.4476	$138.45	$138.45	$138.40
Purchase #6	$165.84	5.561%	$175.0624	$175.06	$175.05	$175.10
Purchase #7	$174.66	5.252%	$183.8331	$183.83	$183.85	$183.80
7 purchase totals =	$959.24		$1,022.2014	$1,022.20	$1,022.25	$1,022.20