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	$170.63	8.680%	$185.4407	$185.44	$185.45	$185.40
Purchase #2	$120.43	6.692%	$128.4892	$128.49	$128.50	$128.50
Purchase #3	$56.65	7.485%	$60.8903	$60.89	$60.90	$60.90
Purchase #4	$89.37	12.124%	$100.2052	$100.21	$100.20	$100.20
Purchase #5	$250.64	11.169%	$278.634	$278.63	$278.65	$278.60
Purchase #6	$142.97	13.745%	$162.6212	$162.62	$162.60	$162.60
Purchase #7	$32.81	10.255%	$36.1747	$36.17	$36.15	$36.20
7 purchase totals =	$863.50		$952.4553	$952.45	$952.45	$952.40