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	$216.31	3.509%	$223.9003	$223.90	$223.90	$223.90
Purchase #2	$145.51	10.141%	$160.2662	$160.27	$160.25	$160.30
Purchase #3	$169.57	12.431%	$190.6492	$190.65	$190.65	$190.60
Purchase #4	$67.65	7.144%	$72.4829	$72.48	$72.50	$72.50
Purchase #5	$209.60	8.641%	$227.7115	$227.71	$227.70	$227.70
Purchase #6	$12.63	5.482%	$13.3224	$13.32	$13.30	$13.30
Purchase #7	$101.45	6.107%	$107.6456	$107.65	$107.65	$107.60
7 purchase totals =	$922.72		$995.9781	$995.98	$995.95	$995.90