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	$205.47	4.583%	$214.8867	$214.89	$214.90	$214.90
Purchase #2	$90.32	6.836%	$96.4943	$96.49	$96.50	$96.50
Purchase #3	$107.66	13.234%	$121.9077	$121.91	$121.90	$121.90
Purchase #4	$27.63	7.143%	$29.6036	$29.60	$29.60	$29.60
Purchase #5	$224.91	9.320%	$245.8716	$245.87	$245.85	$245.90
Purchase #6	$226.26	13.382%	$256.5381	$256.54	$256.55	$256.50
Purchase #7	$78.31	6.151%	$83.1268	$83.13	$83.15	$83.10
7 purchase totals =	$960.56		$1,048.4288	$1,048.43	$1,048.45	$1,048.40