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	$107.50	4.166%	$111.9785	$111.98	$112.00	$112.00
Purchase #2	$44.70	11.487%	$49.8347	$49.83	$49.85	$49.80
Purchase #3	$105.32	12.168%	$118.1353	$118.14	$118.15	$118.10
Purchase #4	$241.46	10.140%	$265.944	$265.94	$265.95	$265.90
Purchase #5	$99.83	5.819%	$105.6391	$105.64	$105.65	$105.60
Purchase #6	$77.91	10.517%	$86.1038	$86.10	$86.10	$86.10
Purchase #7	$192.35	12.642%	$216.6669	$216.67	$216.65	$216.70
7 purchase totals =	$869.07		$954.3023	$954.30	$954.35	$954.20