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	$112.29	13.674%	$127.6445	$127.64	$127.65	$127.60
Purchase #2	$105.43	10.328%	$116.3188	$116.32	$116.30	$116.30
Purchase #3	$32.77	4.168%	$34.1359	$34.14	$34.15	$34.10
Purchase #4	$71.75	6.104%	$76.1296	$76.13	$76.15	$76.10
Purchase #5	$82.82	13.381%	$93.9021	$93.90	$93.90	$93.90
Purchase #6	$140.80	12.603%	$158.545	$158.55	$158.55	$158.50
Purchase #7	$79.97	11.206%	$88.9314	$88.93	$88.95	$88.90
7 purchase totals =	$625.83		$695.6073	$695.61	$695.65	$695.40