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	$166.83	7.648%	$179.5892	$179.59	$179.60	$179.60
Purchase #2	$46.61	8.390%	$50.5206	$50.52	$50.50	$50.50
Purchase #3	$244.50	7.288%	$262.3192	$262.32	$262.30	$262.30
Purchase #4	$82.43	13.111%	$93.2374	$93.24	$93.25	$93.20
Purchase #5	$128.43	4.236%	$133.8703	$133.87	$133.85	$133.90
Purchase #6	$141.77	8.627%	$154.0005	$154.00	$154.00	$154.00
Purchase #7	$85.80	3.606%	$88.8939	$88.89	$88.90	$88.90
7 purchase totals =	$896.37		$962.4311	$962.43	$962.40	$962.40