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	$154.72	4.629%	$161.882	$161.88	$161.90	$161.90
Purchase #2	$118.26	5.389%	$124.633	$124.63	$124.65	$124.60
Purchase #3	$38.45	12.808%	$43.3747	$43.37	$43.35	$43.40
Purchase #4	$238.75	6.547%	$254.381	$254.38	$254.40	$254.40
Purchase #5	$85.88	4.712%	$89.9267	$89.93	$89.95	$89.90
Purchase #6	$59.68	13.127%	$67.5142	$67.51	$67.50	$67.50
Purchase #7	$22.31	5.716%	$23.5852	$23.59	$23.60	$23.60
7 purchase totals =	$718.05		$765.2968	$765.29	$765.35	$765.30