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	$133.63	7.735%	$143.9663	$143.97	$143.95	$144.00
Purchase #2	$37.88	8.765%	$41.2002	$41.20	$41.20	$41.20
Purchase #3	$79.73	13.871%	$90.7893	$90.79	$90.80	$90.80
Purchase #4	$56.35	8.422%	$61.0958	$61.10	$61.10	$61.10
Purchase #5	$9.91	4.637%	$10.3695	$10.37	$10.35	$10.40
Purchase #6	$226.83	6.197%	$240.8867	$240.89	$240.90	$240.90
Purchase #7	$118.45	6.792%	$126.4951	$126.50	$126.50	$126.50
7 purchase totals =	$662.78		$714.8029	$714.82	$714.80	$714.90