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	$11.46	3.561%	$11.8681	$11.87	$11.85	$11.90
Purchase #2	$38.87	4.203%	$40.5037	$40.50	$40.50	$40.50
Purchase #3	$188.52	6.544%	$200.8567	$200.86	$200.85	$200.90
Purchase #4	$173.38	6.470%	$184.5977	$184.60	$184.60	$184.60
Purchase #5	$210.35	11.497%	$234.5339	$234.53	$234.55	$234.50
Purchase #6	$138.62	6.594%	$147.7606	$147.76	$147.75	$147.80
Purchase #7	$19.70	9.397%	$21.5512	$21.55	$21.55	$21.60
7 purchase totals =	$780.90		$841.6719	$841.67	$841.65	$841.80