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	$139.35	12.171%	$156.3103	$156.31	$156.30	$156.30
Purchase #2	$231.51	10.251%	$255.2421	$255.24	$255.25	$255.20
Purchase #3	$49.44	10.178%	$54.472	$54.47	$54.45	$54.50
Purchase #4	$79.78	3.762%	$82.7813	$82.78	$82.80	$82.80
Purchase #5	$214.77	12.228%	$241.0321	$241.03	$241.05	$241.00
Purchase #6	$116.26	6.338%	$123.6286	$123.63	$123.65	$123.60
Purchase #7	$109.78	10.842%	$121.6823	$121.68	$121.70	$121.70
7 purchase totals =	$940.89		$1,035.1487	$1,035.14	$1,035.20	$1,035.10