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	$12.98	9.144%	$14.1669	$14.17	$14.15	$14.20
Purchase #2	$92.45	8.440%	$100.2528	$100.25	$100.25	$100.30
Purchase #3	$113.58	12.682%	$127.9842	$127.98	$128.00	$128.00
Purchase #4	$84.53	4.536%	$88.3643	$88.36	$88.35	$88.40
Purchase #5	$116.98	12.770%	$131.9183	$131.92	$131.90	$131.90
Purchase #6	$107.44	3.522%	$111.224	$111.22	$111.20	$111.20
Purchase #7	$152.38	6.698%	$162.5864	$162.59	$162.60	$162.60
7 purchase totals =	$680.34		$736.4969	$736.49	$736.45	$736.60