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	$144.74	9.747%	$158.8478	$158.85	$158.85	$158.80
Purchase #2	$57.33	13.209%	$64.9027	$64.90	$64.90	$64.90
Purchase #3	$151.70	7.210%	$162.6376	$162.64	$162.65	$162.60
Purchase #4	$119.50	11.598%	$133.3596	$133.36	$133.35	$133.40
Purchase #5	$242.29	12.446%	$272.4454	$272.45	$272.45	$272.40
Purchase #6	$198.46	13.104%	$224.4662	$224.47	$224.45	$224.50
Purchase #7	$48.33	13.340%	$54.7772	$54.78	$54.80	$54.80
7 purchase totals =	$962.35		$1,071.4365	$1,071.45	$1,071.45	$1,071.40