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	$209.89	10.621%	$232.1824	$232.18	$232.20	$232.20
Purchase #2	$178.94	9.674%	$196.2507	$196.25	$196.25	$196.30
Purchase #3	$132.37	5.621%	$139.8105	$139.81	$139.80	$139.80
Purchase #4	$41.85	13.467%	$47.4859	$47.49	$47.50	$47.50
Purchase #5	$233.89	9.626%	$256.4043	$256.40	$256.40	$256.40
Purchase #6	$236.49	9.208%	$258.266	$258.27	$258.25	$258.30
Purchase #7	$113.43	11.440%	$126.4064	$126.41	$126.40	$126.40
7 purchase totals =	$1,146.86		$1,256.8062	$1,256.81	$1,256.80	$1,256.90