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	$138.59	9.462%	$151.7034	$151.70	$151.70	$151.70
Purchase #2	$123.89	8.490%	$134.4083	$134.41	$134.40	$134.40
Purchase #3	$92.48	13.115%	$104.6088	$104.61	$104.60	$104.60
Purchase #4	$36.35	12.335%	$40.8338	$40.83	$40.85	$40.80
Purchase #5	$120.83	9.653%	$132.4937	$132.49	$132.50	$132.50
Purchase #6	$163.91	10.724%	$181.4877	$181.49	$181.50	$181.50
Purchase #7	$90.39	13.176%	$102.2998	$102.30	$102.30	$102.30
7 purchase totals =	$766.44		$847.8355	$847.83	$847.85	$847.80