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	$139.70	7.679%	$150.4276	$150.43	$150.45	$150.40
Purchase #2	$10.97	4.225%	$11.4335	$11.43	$11.45	$11.40
Purchase #3	$125.33	7.351%	$134.543	$134.54	$134.55	$134.50
Purchase #4	$31.25	5.241%	$32.8878	$32.89	$32.90	$32.90
Purchase #5	$179.74	11.795%	$200.9403	$200.94	$200.95	$200.90
Purchase #6	$54.52	12.783%	$61.4893	$61.49	$61.50	$61.50
Purchase #7	$63.41	6.256%	$67.3769	$67.38	$67.40	$67.40
7 purchase totals =	$604.92		$659.0984	$659.10	$659.20	$659.00