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	$157.35	10.132%	$173.2927	$173.29	$173.30	$173.30
Purchase #2	$155.50	13.466%	$176.4396	$176.44	$176.45	$176.40
Purchase #3	$177.49	3.619%	$183.9134	$183.91	$183.90	$183.90
Purchase #4	$69.89	11.791%	$78.1307	$78.13	$78.15	$78.10
Purchase #5	$156.99	8.201%	$169.8647	$169.86	$169.85	$169.90
Purchase #6	$100.86	11.580%	$112.5396	$112.54	$112.55	$112.50
Purchase #7	$163.61	12.105%	$183.415	$183.42	$183.40	$183.40
7 purchase totals =	$981.69		$1,077.5957	$1,077.59	$1,077.60	$1,077.50