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	$194.72	10.774%	$215.6991	$215.70	$215.70	$215.70
Purchase #2	$139.35	6.536%	$148.4579	$148.46	$148.45	$148.50
Purchase #3	$107.94	4.664%	$112.9743	$112.97	$112.95	$113.00
Purchase #4	$49.58	12.169%	$55.6134	$55.61	$55.60	$55.60
Purchase #5	$49.54	7.781%	$53.3947	$53.39	$53.40	$53.40
Purchase #6	$79.35	13.605%	$90.1456	$90.15	$90.15	$90.10
Purchase #7	$234.73	10.163%	$258.5856	$258.59	$258.60	$258.60
7 purchase totals =	$855.21		$934.8706	$934.87	$934.85	$934.90