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	$117.92	8.241%	$127.6378	$127.64	$127.65	$127.60
Purchase #2	$214.47	7.383%	$230.3043	$230.30	$230.30	$230.30
Purchase #3	$143.58	10.366%	$158.4635	$158.46	$158.45	$158.50
Purchase #4	$109.46	5.504%	$115.4847	$115.48	$115.50	$115.50
Purchase #5	$129.92	4.759%	$136.1029	$136.10	$136.10	$136.10
Purchase #6	$218.93	4.725%	$229.2744	$229.27	$229.25	$229.30
Purchase #7	$20.57	3.547%	$21.2996	$21.30	$21.30	$21.30
7 purchase totals =	$954.85		$1,018.5672	$1,018.55	$1,018.55	$1,018.60