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	$242.68	9.402%	$265.4968	$265.50	$265.50	$265.50
Purchase #2	$166.86	5.866%	$176.648	$176.65	$176.65	$176.60
Purchase #3	$211.78	3.870%	$219.9759	$219.98	$220.00	$220.00
Purchase #4	$152.67	7.467%	$164.0699	$164.07	$164.05	$164.10
Purchase #5	$217.85	6.220%	$231.4003	$231.40	$231.40	$231.40
Purchase #6	$86.98	4.160%	$90.5984	$90.60	$90.60	$90.60
Purchase #7	$46.82	4.160%	$48.7677	$48.77	$48.75	$48.80
7 purchase totals =	$1,125.64		$1,196.9570	$1,196.97	$1,196.95	$1,197.00