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	$66.87	8.743%	$72.7164	$72.72	$72.70	$72.70
Purchase #2	$120.59	5.635%	$127.3852	$127.39	$127.40	$127.40
Purchase #3	$18.91	13.534%	$21.4693	$21.47	$21.45	$21.50
Purchase #4	$225.39	10.488%	$249.0289	$249.03	$249.05	$249.00
Purchase #5	$141.68	9.239%	$154.7698	$154.77	$154.75	$154.80
Purchase #6	$224.78	10.697%	$248.8247	$248.82	$248.80	$248.80
Purchase #7	$156.42	9.834%	$171.8023	$171.80	$171.80	$171.80
7 purchase totals =	$954.64		$1,045.9966	$1,046.00	$1,045.95	$1,046.00