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	$164.37	9.600%	$180.1495	$180.15	$180.15	$180.10
Purchase #2	$88.99	11.587%	$99.3013	$99.30	$99.30	$99.30
Purchase #3	$250.26	11.233%	$278.3717	$278.37	$278.35	$278.40
Purchase #4	$87.94	13.279%	$99.6176	$99.62	$99.60	$99.60
Purchase #5	$114.82	9.348%	$125.5534	$125.55	$125.55	$125.60
Purchase #6	$160.30	5.832%	$169.6487	$169.65	$169.65	$169.60
Purchase #7	$175.28	8.862%	$190.8133	$190.81	$190.80	$190.80
7 purchase totals =	$1,041.96		$1,143.4555	$1,143.45	$1,143.40	$1,143.40