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	$143.58	10.552%	$158.7306	$158.73	$158.75	$158.70
Purchase #2	$114.36	9.646%	$125.3912	$125.39	$125.40	$125.40
Purchase #3	$112.89	12.856%	$127.4031	$127.40	$127.40	$127.40
Purchase #4	$38.29	7.124%	$41.0178	$41.02	$41.00	$41.00
Purchase #5	$118.86	6.400%	$126.467	$126.47	$126.45	$126.50
Purchase #6	$140.69	12.492%	$158.265	$158.27	$158.25	$158.30
Purchase #7	$49.93	7.366%	$53.6078	$53.61	$53.60	$53.60
7 purchase totals =	$718.60		$790.8825	$790.89	$790.85	$790.90