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	$211.56	9.152%	$230.922	$230.92	$230.90	$230.90
Purchase #2	$205.60	5.627%	$217.1691	$217.17	$217.15	$217.20
Purchase #3	$57.40	4.173%	$59.7953	$59.80	$59.80	$59.80
Purchase #4	$156.87	4.697%	$164.2382	$164.24	$164.25	$164.20
Purchase #5	$107.69	3.534%	$111.4958	$111.50	$111.50	$111.50
Purchase #6	$43.81	11.845%	$48.9993	$49.00	$49.00	$49.00
Purchase #7	$248.96	6.606%	$265.4063	$265.41	$265.40	$265.40
7 purchase totals =	$1,031.89		$1,098.0260	$1,098.04	$1,098.00	$1,098.00