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	$119.68	6.438%	$127.385	$127.39	$127.40	$127.40
Purchase #2	$159.87	7.339%	$171.6029	$171.60	$171.60	$171.60
Purchase #3	$168.58	5.750%	$178.2734	$178.27	$178.25	$178.30
Purchase #4	$79.70	7.476%	$85.6584	$85.66	$85.65	$85.70
Purchase #5	$52.75	10.806%	$58.4502	$58.45	$58.45	$58.50
Purchase #6	$77.65	5.653%	$82.0396	$82.04	$82.05	$82.00
Purchase #7	$193.75	6.595%	$206.5278	$206.53	$206.55	$206.50
7 purchase totals =	$851.98		$909.9373	$909.94	$909.95	$910.00