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	$161.72	12.435%	$181.8299	$181.83	$181.85	$181.80
Purchase #2	$86.84	10.491%	$95.9504	$95.95	$95.95	$96.00
Purchase #3	$60.52	13.854%	$68.9044	$68.90	$68.90	$68.90
Purchase #4	$39.99	13.183%	$45.2619	$45.26	$45.25	$45.30
Purchase #5	$181.71	10.211%	$200.2644	$200.26	$200.25	$200.30
Purchase #6	$158.73	6.209%	$168.5855	$168.59	$168.60	$168.60
Purchase #7	$64.42	13.208%	$72.9286	$72.93	$72.95	$72.90
7 purchase totals =	$753.93		$833.7251	$833.72	$833.75	$833.80