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	$52.91	12.357%	$59.4481	$59.45	$59.45	$59.40
Purchase #2	$126.85	8.545%	$137.6893	$137.69	$137.70	$137.70
Purchase #3	$182.46	13.719%	$207.4917	$207.49	$207.50	$207.50
Purchase #4	$215.32	12.411%	$242.0434	$242.04	$242.05	$242.00
Purchase #5	$7.72	7.233%	$8.2784	$8.28	$8.30	$8.30
Purchase #6	$248.87	3.116%	$256.6248	$256.62	$256.60	$256.60
Purchase #7	$32.46	4.613%	$33.9574	$33.96	$33.95	$34.00
7 purchase totals =	$866.59		$945.5331	$945.53	$945.55	$945.50