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	$51.55	8.253%	$55.8044	$55.80	$55.80	$55.80
Purchase #2	$208.64	8.859%	$227.1234	$227.12	$227.10	$227.10
Purchase #3	$161.78	9.344%	$176.8967	$176.90	$176.90	$176.90
Purchase #4	$120.83	5.867%	$127.9191	$127.92	$127.90	$127.90
Purchase #5	$151.98	4.211%	$158.3799	$158.38	$158.40	$158.40
Purchase #6	$209.75	3.812%	$217.7457	$217.75	$217.75	$217.70
Purchase #7	$169.93	12.204%	$190.6683	$190.67	$190.65	$190.70
7 purchase totals =	$1,074.46		$1,154.5375	$1,154.54	$1,154.50	$1,154.50