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	$222.51	7.651%	$239.5342	$239.53	$239.55	$239.50
Purchase #2	$54.46	9.751%	$59.7704	$59.77	$59.75	$59.80
Purchase #3	$212.52	10.381%	$234.5817	$234.58	$234.60	$234.60
Purchase #4	$150.83	3.224%	$155.6928	$155.69	$155.70	$155.70
Purchase #5	$46.72	3.722%	$48.4589	$48.46	$48.45	$48.50
Purchase #6	$190.78	3.834%	$198.0945	$198.09	$198.10	$198.10
Purchase #7	$95.52	13.140%	$108.0713	$108.07	$108.05	$108.10
7 purchase totals =	$973.34		$1,044.2038	$1,044.19	$1,044.20	$1,044.30