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	$55.30	11.343%	$61.5727	$61.57	$61.55	$61.60
Purchase #2	$18.27	6.509%	$19.4592	$19.46	$19.45	$19.50
Purchase #3	$115.88	6.278%	$123.1549	$123.15	$123.15	$123.20
Purchase #4	$171.30	8.389%	$185.6704	$185.67	$185.65	$185.70
Purchase #5	$163.54	11.707%	$182.6856	$182.69	$182.70	$182.70
Purchase #6	$99.52	6.458%	$105.947	$105.95	$105.95	$105.90
Purchase #7	$52.89	10.484%	$58.435	$58.44	$58.45	$58.40
7 purchase totals =	$676.70		$736.9248	$736.93	$736.90	$737.00