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	$48.42	8.321%	$52.449	$52.45	$52.45	$52.40
Purchase #2	$226.72	5.331%	$238.8064	$238.81	$238.80	$238.80
Purchase #3	$237.67	5.377%	$250.4495	$250.45	$250.45	$250.40
Purchase #4	$30.88	7.274%	$33.1262	$33.13	$33.15	$33.10
Purchase #5	$250.43	10.804%	$277.4865	$277.49	$277.50	$277.50
Purchase #6	$32.55	12.369%	$36.5761	$36.58	$36.60	$36.60
Purchase #7	$241.83	4.143%	$251.849	$251.85	$251.85	$251.80
7 purchase totals =	$1,068.50		$1,140.7427	$1,140.76	$1,140.80	$1,140.60