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	$159.57	7.526%	$171.5792	$171.58	$171.60	$171.60
Purchase #2	$218.86	6.262%	$232.565	$232.57	$232.55	$232.60
Purchase #3	$72.88	7.871%	$78.6164	$78.62	$78.60	$78.60
Purchase #4	$239.59	7.680%	$257.9905	$257.99	$258.00	$258.00
Purchase #5	$47.94	7.261%	$51.4209	$51.42	$51.40	$51.40
Purchase #6	$247.64	7.235%	$265.5568	$265.56	$265.55	$265.60
Purchase #7	$39.80	4.408%	$41.5544	$41.55	$41.55	$41.60
7 purchase totals =	$1,026.28		$1,099.2832	$1,099.29	$1,099.25	$1,099.40