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	$241.42	7.528%	$259.5941	$259.59	$259.60	$259.60
Purchase #2	$97.29	8.432%	$105.4935	$105.49	$105.50	$105.50
Purchase #3	$105.69	6.534%	$112.5958	$112.60	$112.60	$112.60
Purchase #4	$137.42	10.613%	$152.0044	$152.00	$152.00	$152.00
Purchase #5	$108.36	8.105%	$117.1426	$117.14	$117.15	$117.10
Purchase #6	$104.95	9.686%	$115.1155	$115.12	$115.10	$115.10
Purchase #7	$186.64	5.360%	$196.6439	$196.64	$196.65	$196.60
7 purchase totals =	$981.77		$1,058.5898	$1,058.58	$1,058.60	$1,058.50