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	$102.81	8.149%	$111.188	$111.19	$111.20	$111.20
Purchase #2	$23.51	9.596%	$25.766	$25.77	$25.75	$25.80
Purchase #3	$145.25	4.867%	$152.3193	$152.32	$152.30	$152.30
Purchase #4	$123.66	3.127%	$127.5268	$127.53	$127.55	$127.50
Purchase #5	$248.29	5.650%	$262.3184	$262.32	$262.30	$262.30
Purchase #6	$176.65	10.828%	$195.7777	$195.78	$195.80	$195.80
Purchase #7	$101.63	3.296%	$104.9797	$104.98	$105.00	$105.00
7 purchase totals =	$921.80		$979.8759	$979.89	$979.90	$979.90