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	$178.59	8.632%	$194.0059	$194.01	$194.00	$194.00
Purchase #2	$111.33	11.320%	$123.9326	$123.93	$123.95	$123.90
Purchase #3	$138.98	6.716%	$148.3139	$148.31	$148.30	$148.30
Purchase #4	$113.70	11.139%	$126.365	$126.37	$126.35	$126.40
Purchase #5	$140.50	12.772%	$158.4447	$158.44	$158.45	$158.40
Purchase #6	$50.90	5.157%	$53.5249	$53.52	$53.50	$53.50
Purchase #7	$176.26	5.386%	$185.7534	$185.75	$185.75	$185.80
7 purchase totals =	$910.26		$990.3404	$990.33	$990.30	$990.30