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	$49.97	9.304%	$54.6192	$54.62	$54.60	$54.60
Purchase #2	$101.81	7.497%	$109.4427	$109.44	$109.45	$109.40
Purchase #3	$214.51	6.255%	$227.9276	$227.93	$227.95	$227.90
Purchase #4	$17.49	5.565%	$18.4633	$18.46	$18.45	$18.50
Purchase #5	$91.56	3.308%	$94.5888	$94.59	$94.60	$94.60
Purchase #6	$20.28	5.510%	$21.3974	$21.40	$21.40	$21.40
Purchase #7	$181.28	9.511%	$198.5215	$198.52	$198.50	$198.50
7 purchase totals =	$676.90		$724.9605	$724.96	$724.95	$724.90