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	$224.30	4.166%	$233.6443	$233.64	$233.65	$233.60
Purchase #2	$102.37	8.824%	$111.4031	$111.40	$111.40	$111.40
Purchase #3	$161.37	7.814%	$173.9795	$173.98	$174.00	$174.00
Purchase #4	$14.32	3.576%	$14.8321	$14.83	$14.85	$14.80
Purchase #5	$139.83	8.138%	$151.2094	$151.21	$151.20	$151.20
Purchase #6	$100.87	4.340%	$105.2478	$105.25	$105.25	$105.20
Purchase #7	$220.25	3.410%	$227.7605	$227.76	$227.75	$227.80
7 purchase totals =	$963.31		$1,018.0767	$1,018.07	$1,018.10	$1,018.00