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	$123.89	5.325%	$130.4871	$130.49	$130.50	$130.50
Purchase #2	$58.96	11.516%	$65.7498	$65.75	$65.75	$65.70
Purchase #3	$234.69	8.217%	$253.9745	$253.97	$253.95	$254.00
Purchase #4	$99.47	12.365%	$111.7695	$111.77	$111.75	$111.80
Purchase #5	$46.57	4.216%	$48.5334	$48.53	$48.55	$48.50
Purchase #6	$41.40	3.857%	$42.9968	$43.00	$43.00	$43.00
Purchase #7	$109.83	12.537%	$123.5994	$123.60	$123.60	$123.60
7 purchase totals =	$714.81		$777.1105	$777.11	$777.10	$777.10