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	$22.66	12.812%	$25.5632	$25.56	$25.55	$25.60
Purchase #2	$233.29	8.241%	$252.5154	$252.52	$252.50	$252.50
Purchase #3	$126.51	3.741%	$131.2427	$131.24	$131.25	$131.20
Purchase #4	$133.65	4.654%	$139.8701	$139.87	$139.85	$139.90
Purchase #5	$182.42	4.439%	$190.5176	$190.52	$190.50	$190.50
Purchase #6	$212.84	12.433%	$239.3024	$239.30	$239.30	$239.30
Purchase #7	$60.90	10.247%	$67.1404	$67.14	$67.15	$67.10
7 purchase totals =	$972.27		$1,046.1518	$1,046.15	$1,046.10	$1,046.10