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	$162.66	12.290%	$182.6509	$182.65	$182.65	$182.70
Purchase #2	$34.30	8.238%	$37.1256	$37.13	$37.15	$37.10
Purchase #3	$127.41	3.599%	$131.9955	$132.00	$132.00	$132.00
Purchase #4	$71.78	5.555%	$75.7674	$75.77	$75.75	$75.80
Purchase #5	$32.94	5.732%	$34.8281	$34.83	$34.85	$34.80
Purchase #6	$230.75	10.729%	$255.5072	$255.51	$255.50	$255.50
Purchase #7	$11.39	10.830%	$12.6235	$12.62	$12.60	$12.60
7 purchase totals =	$671.23		$730.4982	$730.51	$730.50	$730.50