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	$119.42	5.203%	$125.6334	$125.63	$125.65	$125.60
Purchase #2	$248.88	12.504%	$280	$280.00	$280.00	$280.00
Purchase #3	$117.79	8.475%	$127.7727	$127.77	$127.75	$127.80
Purchase #4	$156.48	10.805%	$173.3877	$173.39	$173.40	$173.40
Purchase #5	$210.71	13.102%	$238.3172	$238.32	$238.30	$238.30
Purchase #6	$195.78	12.509%	$220.2701	$220.27	$220.25	$220.30
Purchase #7	$6.79	8.612%	$7.3748	$7.37	$7.35	$7.40
7 purchase totals =	$1,055.85		$1,172.7559	$1,172.75	$1,172.70	$1,172.80