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	$89.43	7.143%	$95.818	$95.82	$95.80	$95.80
Purchase #2	$137.52	5.201%	$144.6724	$144.67	$144.65	$144.70
Purchase #3	$68.84	6.520%	$73.3284	$73.33	$73.35	$73.30
Purchase #4	$53.42	13.751%	$60.7658	$60.77	$60.75	$60.80
Purchase #5	$229.59	11.259%	$255.4395	$255.44	$255.45	$255.40
Purchase #6	$170.38	10.256%	$187.8542	$187.85	$187.85	$187.90
Purchase #7	$124.67	11.359%	$138.8313	$138.83	$138.85	$138.80
7 purchase totals =	$873.85		$956.7096	$956.71	$956.70	$956.70