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	$168.56	7.147%	$180.607	$180.61	$180.60	$180.60
Purchase #2	$48.42	6.568%	$51.6002	$51.60	$51.60	$51.60
Purchase #3	$121.78	13.397%	$138.0949	$138.09	$138.10	$138.10
Purchase #4	$110.97	7.151%	$118.9055	$118.91	$118.90	$118.90
Purchase #5	$131.64	11.857%	$147.2486	$147.25	$147.25	$147.20
Purchase #6	$80.87	5.673%	$85.4578	$85.46	$85.45	$85.50
Purchase #7	$160.39	11.239%	$178.4162	$178.42	$178.40	$178.40
7 purchase totals =	$822.63		$900.3302	$900.34	$900.30	$900.30