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	$191.94	4.346%	$200.2817	$200.28	$200.30	$200.30
Purchase #2	$208.72	11.396%	$232.5057	$232.51	$232.50	$232.50
Purchase #3	$62.81	13.523%	$71.3038	$71.30	$71.30	$71.30
Purchase #4	$232.86	8.845%	$253.4565	$253.46	$253.45	$253.50
Purchase #5	$187.57	10.390%	$207.0585	$207.06	$207.05	$207.10
Purchase #6	$29.61	6.381%	$31.4994	$31.50	$31.50	$31.50
Purchase #7	$29.81	12.238%	$33.4581	$33.46	$33.45	$33.50
7 purchase totals =	$943.32		$1,029.5637	$1,029.57	$1,029.55	$1,029.70