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	$242.75	7.798%	$261.6796	$261.68	$261.70	$261.70
Purchase #2	$149.79	8.363%	$162.3169	$162.32	$162.30	$162.30
Purchase #3	$50.82	6.115%	$53.9276	$53.93	$53.95	$53.90
Purchase #4	$31.49	3.873%	$32.7096	$32.71	$32.70	$32.70
Purchase #5	$66.38	9.106%	$72.4246	$72.42	$72.40	$72.40
Purchase #6	$105.94	5.662%	$111.9383	$111.94	$111.95	$111.90
Purchase #7	$12.57	5.491%	$13.2602	$13.26	$13.25	$13.30
7 purchase totals =	$659.74		$708.2568	$708.26	$708.25	$708.20