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	$150.28	3.753%	$155.92	$155.92	$155.90	$155.90
Purchase #2	$157.25	12.353%	$176.6751	$176.68	$176.70	$176.70
Purchase #3	$131.64	4.478%	$137.5348	$137.53	$137.55	$137.50
Purchase #4	$210.61	13.423%	$238.8802	$238.88	$238.90	$238.90
Purchase #5	$68.86	13.856%	$78.4012	$78.40	$78.40	$78.40
Purchase #6	$35.91	12.785%	$40.5011	$40.50	$40.50	$40.50
Purchase #7	$205.29	5.654%	$216.8971	$216.90	$216.90	$216.90
7 purchase totals =	$959.84		$1,044.8095	$1,044.81	$1,044.85	$1,044.80