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	$96.83	7.576%	$104.1658	$104.17	$104.15	$104.20
Purchase #2	$246.60	3.614%	$255.5121	$255.51	$255.50	$255.50
Purchase #3	$225.51	5.303%	$237.4688	$237.47	$237.45	$237.50
Purchase #4	$20.52	8.217%	$22.2061	$22.21	$22.20	$22.20
Purchase #5	$104.87	12.690%	$118.178	$118.18	$118.20	$118.20
Purchase #6	$189.51	4.390%	$197.8295	$197.83	$197.85	$197.80
Purchase #7	$54.85	8.638%	$59.5879	$59.59	$59.60	$59.60
7 purchase totals =	$938.69		$994.9482	$994.96	$994.95	$995.00