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	$151.30	3.723%	$156.9329	$156.93	$156.95	$156.90
Purchase #2	$226.69	5.695%	$239.6	$239.60	$239.60	$239.60
Purchase #3	$32.42	3.105%	$33.4266	$33.43	$33.45	$33.40
Purchase #4	$95.29	10.493%	$105.2888	$105.29	$105.30	$105.30
Purchase #5	$92.77	8.318%	$100.4866	$100.49	$100.50	$100.50
Purchase #6	$22.26	12.143%	$24.963	$24.96	$24.95	$25.00
Purchase #7	$147.54	7.335%	$158.3621	$158.36	$158.35	$158.40
7 purchase totals =	$768.27		$819.0600	$819.06	$819.10	$819.10