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	$142.89	5.551%	$150.8218	$150.82	$150.80	$150.80
Purchase #2	$163.89	5.765%	$173.3383	$173.34	$173.35	$173.30
Purchase #3	$12.76	3.773%	$13.2414	$13.24	$13.25	$13.20
Purchase #4	$237.81	6.217%	$252.5946	$252.59	$252.60	$252.60
Purchase #5	$84.33	7.558%	$90.7037	$90.70	$90.70	$90.70
Purchase #6	$66.99	7.406%	$71.9513	$71.95	$71.95	$72.00
Purchase #7	$118.92	8.379%	$128.8843	$128.88	$128.90	$128.90
7 purchase totals =	$827.59		$881.5354	$881.52	$881.55	$881.50