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	$143.81	6.857%	$153.6711	$153.67	$153.65	$153.70
Purchase #2	$41.30	12.508%	$46.4658	$46.47	$46.45	$46.50
Purchase #3	$162.60	10.561%	$179.7722	$179.77	$179.75	$179.80
Purchase #4	$202.77	6.439%	$215.8264	$215.83	$215.85	$215.80
Purchase #5	$182.82	8.398%	$198.1732	$198.17	$198.15	$198.20
Purchase #6	$98.37	7.160%	$105.4133	$105.41	$105.40	$105.40
Purchase #7	$93.86	5.724%	$99.2325	$99.23	$99.25	$99.20
7 purchase totals =	$925.53		$998.5545	$998.55	$998.50	$998.60