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	$156.92	5.320%	$165.2681	$165.27	$165.25	$165.30
Purchase #2	$129.51	12.360%	$145.5174	$145.52	$145.50	$145.50
Purchase #3	$99.86	11.817%	$111.6605	$111.66	$111.65	$111.70
Purchase #4	$24.48	3.500%	$25.3368	$25.34	$25.35	$25.30
Purchase #5	$152.57	11.831%	$170.6206	$170.62	$170.60	$170.60
Purchase #6	$162.72	5.184%	$171.1554	$171.16	$171.15	$171.20
Purchase #7	$30.37	8.440%	$32.9332	$32.93	$32.95	$32.90
7 purchase totals =	$756.43		$822.4920	$822.50	$822.45	$822.50