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	$58.77	5.635%	$62.0817	$62.08	$62.10	$62.10
Purchase #2	$74.32	5.784%	$78.6187	$78.62	$78.60	$78.60
Purchase #3	$170.82	5.285%	$179.8478	$179.85	$179.85	$179.80
Purchase #4	$112.57	10.329%	$124.1974	$124.20	$124.20	$124.20
Purchase #5	$107.34	7.321%	$115.1984	$115.20	$115.20	$115.20
Purchase #6	$244.35	4.632%	$255.6683	$255.67	$255.65	$255.70
Purchase #7	$131.50	8.436%	$142.5933	$142.59	$142.60	$142.60
7 purchase totals =	$899.67		$958.2056	$958.21	$958.20	$958.20