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	$240.28	12.172%	$269.5269	$269.53	$269.55	$269.50
Purchase #2	$147.67	4.230%	$153.9164	$153.92	$153.90	$153.90
Purchase #3	$51.77	4.530%	$54.1152	$54.12	$54.10	$54.10
Purchase #4	$160.67	13.171%	$181.8318	$181.83	$181.85	$181.80
Purchase #5	$95.55	8.664%	$103.8285	$103.83	$103.85	$103.80
Purchase #6	$116.43	5.792%	$123.1736	$123.17	$123.15	$123.20
Purchase #7	$241.36	8.625%	$262.1773	$262.18	$262.20	$262.20
7 purchase totals =	$1,053.73		$1,148.5697	$1,148.58	$1,148.60	$1,148.50