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	$88.76	13.146%	$100.4284	$100.43	$100.45	$100.40
Purchase #2	$172.39	5.513%	$181.8939	$181.89	$181.90	$181.90
Purchase #3	$7.32	3.569%	$7.5813	$7.58	$7.60	$7.60
Purchase #4	$82.98	5.540%	$87.5771	$87.58	$87.60	$87.60
Purchase #5	$69.75	7.866%	$75.2365	$75.24	$75.25	$75.20
Purchase #6	$96.90	4.713%	$101.4669	$101.47	$101.45	$101.50
Purchase #7	$109.54	12.189%	$122.8918	$122.89	$122.90	$122.90
7 purchase totals =	$627.64		$677.0759	$677.08	$677.15	$677.10