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	$14.37	12.639%	$16.1862	$16.19	$16.20	$16.20
Purchase #2	$214.42	4.233%	$223.4964	$223.50	$223.50	$223.50
Purchase #3	$81.68	4.528%	$85.3785	$85.38	$85.40	$85.40
Purchase #4	$208.42	5.692%	$220.2833	$220.28	$220.30	$220.30
Purchase #5	$122.30	4.208%	$127.4464	$127.45	$127.45	$127.40
Purchase #6	$132.43	12.345%	$148.7785	$148.78	$148.80	$148.80
Purchase #7	$58.90	9.119%	$64.2711	$64.27	$64.25	$64.30
7 purchase totals =	$832.52		$885.8404	$885.85	$885.90	$885.90