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	$178.32	11.772%	$199.3118	$199.31	$199.30	$199.30
Purchase #2	$208.85	6.161%	$221.7172	$221.72	$221.70	$221.70
Purchase #3	$193.27	13.400%	$219.1682	$219.17	$219.15	$219.20
Purchase #4	$56.95	7.273%	$61.092	$61.09	$61.10	$61.10
Purchase #5	$41.64	9.378%	$45.545	$45.55	$45.55	$45.50
Purchase #6	$26.83	9.611%	$29.4086	$29.41	$29.40	$29.40
Purchase #7	$34.92	11.308%	$38.8688	$38.87	$38.85	$38.90
7 purchase totals =	$740.78		$815.1116	$815.12	$815.05	$815.10