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	$95.26	13.523%	$108.142	$108.14	$108.15	$108.10
Purchase #2	$90.77	9.549%	$99.4376	$99.44	$99.45	$99.40
Purchase #3	$86.82	11.614%	$96.9033	$96.90	$96.90	$96.90
Purchase #4	$10.60	11.178%	$11.7849	$11.78	$11.80	$11.80
Purchase #5	$104.68	10.145%	$115.2998	$115.30	$115.30	$115.30
Purchase #6	$84.64	5.538%	$89.3274	$89.33	$89.35	$89.30
Purchase #7	$94.26	6.255%	$100.156	$100.16	$100.15	$100.20
7 purchase totals =	$567.03		$621.0510	$621.05	$621.10	$621.00