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	$148.85	6.694%	$158.814	$158.81	$158.80	$158.80
Purchase #2	$227.94	13.844%	$259.496	$259.50	$259.50	$259.50
Purchase #3	$131.71	4.737%	$137.9491	$137.95	$137.95	$137.90
Purchase #4	$146.27	6.301%	$155.4865	$155.49	$155.50	$155.50
Purchase #5	$103.98	7.143%	$111.4073	$111.41	$111.40	$111.40
Purchase #6	$94.32	8.156%	$102.0127	$102.01	$102.00	$102.00
Purchase #7	$138.83	10.104%	$152.8574	$152.86	$152.85	$152.90
7 purchase totals =	$991.90		$1,078.0230	$1,078.03	$1,078.00	$1,078.00