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	$112.69	5.719%	$119.1347	$119.13	$119.15	$119.10
Purchase #2	$132.46	9.405%	$144.9179	$144.92	$144.90	$144.90
Purchase #3	$241.38	12.721%	$272.0859	$272.09	$272.10	$272.10
Purchase #4	$215.95	3.768%	$224.087	$224.09	$224.10	$224.10
Purchase #5	$172.52	4.175%	$179.7227	$179.72	$179.70	$179.70
Purchase #6	$128.59	13.255%	$145.6346	$145.63	$145.65	$145.60
Purchase #7	$54.75	3.843%	$56.854	$56.85	$56.85	$56.90
7 purchase totals =	$1,058.34		$1,142.4368	$1,142.43	$1,142.45	$1,142.40