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	$227.46	9.715%	$249.5577	$249.56	$249.55	$249.60
Purchase #2	$82.70	3.767%	$85.8153	$85.82	$85.80	$85.80
Purchase #3	$9.96	11.169%	$11.0724	$11.07	$11.05	$11.10
Purchase #4	$244.96	4.435%	$255.824	$255.82	$255.80	$255.80
Purchase #5	$131.34	13.254%	$148.7478	$148.75	$148.75	$148.70
Purchase #6	$227.52	13.620%	$258.5082	$258.51	$258.50	$258.50
Purchase #7	$32.88	5.153%	$34.5743	$34.57	$34.55	$34.60
7 purchase totals =	$956.82		$1,044.0997	$1,044.10	$1,044.00	$1,044.10