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	$95.96	3.742%	$99.5508	$99.55	$99.55	$99.60
Purchase #2	$56.42	7.856%	$60.8524	$60.85	$60.85	$60.90
Purchase #3	$61.76	6.360%	$65.6879	$65.69	$65.70	$65.70
Purchase #4	$115.25	10.692%	$127.5725	$127.57	$127.55	$127.60
Purchase #5	$165.26	11.339%	$183.9988	$184.00	$184.00	$184.00
Purchase #6	$28.59	4.643%	$29.9174	$29.92	$29.90	$29.90
Purchase #7	$116.43	8.840%	$126.7224	$126.72	$126.70	$126.70
7 purchase totals =	$639.67		$694.3022	$694.30	$694.25	$694.40