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	$51.93	13.654%	$59.0205	$59.02	$59.00	$59.00
Purchase #2	$10.89	13.368%	$12.3458	$12.35	$12.35	$12.30
Purchase #3	$128.38	12.391%	$144.2876	$144.29	$144.30	$144.30
Purchase #4	$145.95	12.224%	$163.7909	$163.79	$163.80	$163.80
Purchase #5	$60.45	3.519%	$62.5772	$62.58	$62.60	$62.60
Purchase #6	$117.86	8.758%	$128.1822	$128.18	$128.20	$128.20
Purchase #7	$248.86	8.328%	$269.5851	$269.59	$269.60	$269.60
7 purchase totals =	$764.32		$839.7893	$839.80	$839.85	$839.80