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	$137.72	10.422%	$152.0732	$152.07	$152.05	$152.10
Purchase #2	$61.60	13.752%	$70.0712	$70.07	$70.05	$70.10
Purchase #3	$120.29	9.261%	$131.4301	$131.43	$131.45	$131.40
Purchase #4	$60.73	4.716%	$63.594	$63.59	$63.60	$63.60
Purchase #5	$42.84	7.629%	$46.1083	$46.11	$46.10	$46.10
Purchase #6	$168.57	7.843%	$181.7909	$181.79	$181.80	$181.80
Purchase #7	$130.93	7.717%	$141.0339	$141.03	$141.05	$141.00
7 purchase totals =	$722.68		$786.1016	$786.09	$786.10	$786.10