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	$127.39	13.121%	$144.1048	$144.10	$144.10	$144.10
Purchase #2	$40.43	5.421%	$42.6217	$42.62	$42.60	$42.60
Purchase #3	$24.38	3.111%	$25.1385	$25.14	$25.15	$25.10
Purchase #4	$151.85	13.725%	$172.6914	$172.69	$172.70	$172.70
Purchase #5	$210.39	9.287%	$229.9289	$229.93	$229.95	$229.90
Purchase #6	$49.33	13.233%	$55.8578	$55.86	$55.85	$55.90
Purchase #7	$116.45	8.272%	$126.0827	$126.08	$126.10	$126.10
7 purchase totals =	$720.22		$796.4258	$796.42	$796.45	$796.40