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	$45.38	6.482%	$48.3215	$48.32	$48.30	$48.30
Purchase #2	$225.70	13.673%	$256.56	$256.56	$256.55	$256.60
Purchase #3	$169.56	6.520%	$180.6153	$180.62	$180.60	$180.60
Purchase #4	$179.72	11.466%	$200.3267	$200.33	$200.35	$200.30
Purchase #5	$203.60	10.705%	$225.3954	$225.40	$225.40	$225.40
Purchase #6	$187.78	13.256%	$212.6721	$212.67	$212.65	$212.70
Purchase #7	$241.79	7.147%	$259.0707	$259.07	$259.05	$259.10
7 purchase totals =	$1,253.53		$1,382.9617	$1,382.97	$1,382.90	$1,383.00