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	$148.94	6.867%	$159.1677	$159.17	$159.15	$159.20
Purchase #2	$77.58	10.639%	$85.8337	$85.83	$85.85	$85.80
Purchase #3	$43.55	13.485%	$49.4227	$49.42	$49.40	$49.40
Purchase #4	$107.64	3.609%	$111.5247	$111.52	$111.50	$111.50
Purchase #5	$148.25	11.536%	$165.3521	$165.35	$165.35	$165.40
Purchase #6	$163.79	7.185%	$175.5583	$175.56	$175.55	$175.60
Purchase #7	$140.80	7.668%	$151.5965	$151.60	$151.60	$151.60
7 purchase totals =	$830.55		$898.4557	$898.45	$898.40	$898.50