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	$42.69	9.765%	$46.8587	$46.86	$46.85	$46.90
Purchase #2	$61.97	7.338%	$66.5174	$66.52	$66.50	$66.50
Purchase #3	$42.76	6.376%	$45.4864	$45.49	$45.50	$45.50
Purchase #4	$172.68	3.473%	$178.6772	$178.68	$178.70	$178.70
Purchase #5	$45.43	4.110%	$47.2972	$47.30	$47.30	$47.30
Purchase #6	$84.26	5.652%	$89.0224	$89.02	$89.00	$89.00
Purchase #7	$228.60	12.651%	$257.5202	$257.52	$257.50	$257.50
7 purchase totals =	$678.39		$731.3795	$731.39	$731.35	$731.40