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	$54.97	7.484%	$59.084	$59.08	$59.10	$59.10
Purchase #2	$78.68	6.752%	$83.9925	$83.99	$84.00	$84.00
Purchase #3	$153.46	7.201%	$164.5107	$164.51	$164.50	$164.50
Purchase #4	$90.50	6.741%	$96.6006	$96.60	$96.60	$96.60
Purchase #5	$83.42	13.685%	$94.836	$94.84	$94.85	$94.80
Purchase #6	$57.61	10.158%	$63.462	$63.46	$63.45	$63.50
Purchase #7	$51.63	3.230%	$53.2976	$53.30	$53.30	$53.30
7 purchase totals =	$570.27		$615.7834	$615.78	$615.80	$615.80