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	$226.70	5.302%	$238.7196	$238.72	$238.70	$238.70
Purchase #2	$88.70	4.237%	$92.4582	$92.46	$92.45	$92.50
Purchase #3	$17.69	7.725%	$19.0566	$19.06	$19.05	$19.10
Purchase #4	$68.29	6.761%	$72.9071	$72.91	$72.90	$72.90
Purchase #5	$240.33	7.205%	$257.6458	$257.65	$257.65	$257.60
Purchase #6	$105.91	5.461%	$111.6937	$111.69	$111.70	$111.70
Purchase #7	$38.40	10.158%	$42.3007	$42.30	$42.30	$42.30
7 purchase totals =	$786.02		$834.7817	$834.79	$834.75	$834.80