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	$174.80	6.180%	$185.6026	$185.60	$185.60	$185.60
Purchase #2	$127.75	12.391%	$143.5795	$143.58	$143.60	$143.60
Purchase #3	$214.42	8.119%	$231.8288	$231.83	$231.85	$231.80
Purchase #4	$183.54	4.828%	$192.4013	$192.40	$192.40	$192.40
Purchase #5	$43.99	7.306%	$47.2039	$47.20	$47.20	$47.20
Purchase #6	$49.63	9.569%	$54.3791	$54.38	$54.40	$54.40
Purchase #7	$178.61	12.288%	$200.5576	$200.56	$200.55	$200.60
7 purchase totals =	$972.74		$1,055.5528	$1,055.55	$1,055.60	$1,055.60