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	$228.60	11.753%	$255.4674	$255.47	$255.45	$255.50
Purchase #2	$74.70	8.230%	$80.8478	$80.85	$80.85	$80.80
Purchase #3	$137.61	10.405%	$151.9283	$151.93	$151.95	$151.90
Purchase #4	$239.82	7.368%	$257.4899	$257.49	$257.50	$257.50
Purchase #5	$46.55	8.729%	$50.6133	$50.61	$50.60	$50.60
Purchase #6	$237.39	11.324%	$264.272	$264.27	$264.25	$264.30
Purchase #7	$6.97	10.533%	$7.7042	$7.70	$7.70	$7.70
7 purchase totals =	$971.64		$1,068.3229	$1,068.32	$1,068.30	$1,068.30