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	$222.54	5.379%	$234.5104	$234.51	$234.50	$234.50
Purchase #2	$89.62	4.657%	$93.7936	$93.79	$93.80	$93.80
Purchase #3	$81.25	13.494%	$92.2139	$92.21	$92.20	$92.20
Purchase #4	$147.65	10.174%	$162.6719	$162.67	$162.65	$162.70
Purchase #5	$118.40	7.387%	$127.1462	$127.15	$127.15	$127.10
Purchase #6	$99.81	3.778%	$103.5808	$103.58	$103.60	$103.60
Purchase #7	$109.47	9.122%	$119.4559	$119.46	$119.45	$119.50
7 purchase totals =	$868.74		$933.3727	$933.37	$933.35	$933.40