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	$104.32	11.275%	$116.0821	$116.08	$116.10	$116.10
Purchase #2	$105.61	5.139%	$111.0373	$111.04	$111.05	$111.00
Purchase #3	$237.98	11.235%	$264.7171	$264.72	$264.70	$264.70
Purchase #4	$146.32	9.236%	$159.8341	$159.83	$159.85	$159.80
Purchase #5	$10.70	6.263%	$11.3701	$11.37	$11.35	$11.40
Purchase #6	$92.42	9.733%	$101.4152	$101.42	$101.40	$101.40
Purchase #7	$135.36	4.549%	$141.5175	$141.52	$141.50	$141.50
7 purchase totals =	$832.71		$905.9734	$905.98	$905.95	$905.90