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	$188.78	9.697%	$207.086	$207.09	$207.10	$207.10
Purchase #2	$171.59	11.215%	$190.8338	$190.83	$190.85	$190.80
Purchase #3	$122.78	4.650%	$128.4893	$128.49	$128.50	$128.50
Purchase #4	$126.90	8.642%	$137.8667	$137.87	$137.85	$137.90
Purchase #5	$100.34	6.246%	$106.6072	$106.61	$106.60	$106.60
Purchase #6	$166.85	12.218%	$187.2357	$187.24	$187.25	$187.20
Purchase #7	$156.32	10.262%	$172.3616	$172.36	$172.35	$172.40
7 purchase totals =	$1,033.56		$1,130.4803	$1,130.49	$1,130.50	$1,130.50