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	$234.47	10.185%	$258.3508	$258.35	$258.35	$258.40
Purchase #2	$138.86	9.423%	$151.9448	$151.94	$151.95	$151.90
Purchase #3	$100.88	10.663%	$111.6368	$111.64	$111.65	$111.60
Purchase #4	$233.85	3.351%	$241.6863	$241.69	$241.70	$241.70
Purchase #5	$41.31	10.831%	$45.7843	$45.78	$45.80	$45.80
Purchase #6	$59.45	8.342%	$64.4093	$64.41	$64.40	$64.40
Purchase #7	$85.78	5.871%	$90.8161	$90.82	$90.80	$90.80
7 purchase totals =	$894.60		$964.6284	$964.63	$964.65	$964.60