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	$13.75	5.834%	$14.5522	$14.55	$14.55	$14.60
Purchase #2	$249.77	7.409%	$268.2755	$268.28	$268.30	$268.30
Purchase #3	$71.89	10.772%	$79.634	$79.63	$79.65	$79.60
Purchase #4	$50.54	8.714%	$54.9441	$54.94	$54.95	$54.90
Purchase #5	$243.69	11.451%	$271.5949	$271.59	$271.60	$271.60
Purchase #6	$166.34	11.835%	$186.0263	$186.03	$186.05	$186.00
Purchase #7	$177.87	10.684%	$196.8736	$196.87	$196.85	$196.90
7 purchase totals =	$973.85		$1,071.9006	$1,071.89	$1,071.95	$1,071.90