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	$38.51	5.149%	$40.4929	$40.49	$40.50	$40.50
Purchase #2	$49.34	10.852%	$54.6944	$54.69	$54.70	$54.70
Purchase #3	$76.42	4.173%	$79.609	$79.61	$79.60	$79.60
Purchase #4	$179.64	7.720%	$193.5082	$193.51	$193.50	$193.50
Purchase #5	$241.56	6.228%	$256.6044	$256.60	$256.60	$256.60
Purchase #6	$151.27	7.210%	$162.1766	$162.18	$162.20	$162.20
Purchase #7	$218.67	5.630%	$230.9811	$230.98	$231.00	$231.00
7 purchase totals =	$955.41		$1,018.0666	$1,018.06	$1,018.10	$1,018.10