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	$173.53	5.382%	$182.8694	$182.87	$182.85	$182.90
Purchase #2	$53.37	4.670%	$55.8624	$55.86	$55.85	$55.90
Purchase #3	$105.25	8.339%	$114.0268	$114.03	$114.05	$114.00
Purchase #4	$37.37	13.418%	$42.3843	$42.38	$42.40	$42.40
Purchase #5	$146.93	3.275%	$151.742	$151.74	$151.75	$151.70
Purchase #6	$173.55	7.587%	$186.7172	$186.72	$186.70	$186.70
Purchase #7	$169.91	7.509%	$182.6685	$182.67	$182.65	$182.70
7 purchase totals =	$859.91		$916.2706	$916.27	$916.25	$916.30