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	$155.77	10.141%	$171.5666	$171.57	$171.55	$171.60
Purchase #2	$85.64	10.490%	$94.6236	$94.62	$94.60	$94.60
Purchase #3	$111.97	5.590%	$118.2291	$118.23	$118.25	$118.20
Purchase #4	$56.95	8.721%	$61.9166	$61.92	$61.90	$61.90
Purchase #5	$140.49	9.459%	$153.7789	$153.78	$153.80	$153.80
Purchase #6	$75.31	8.764%	$81.9102	$81.91	$81.90	$81.90
Purchase #7	$50.80	7.324%	$54.5206	$54.52	$54.50	$54.50
7 purchase totals =	$676.93		$736.5456	$736.55	$736.50	$736.50