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	$230.82	10.238%	$254.4514	$254.45	$254.45	$254.50
Purchase #2	$242.63	3.808%	$251.8694	$251.87	$251.85	$251.90
Purchase #3	$178.52	6.690%	$190.463	$190.46	$190.45	$190.50
Purchase #4	$109.90	11.543%	$122.5858	$122.59	$122.60	$122.60
Purchase #5	$75.96	12.812%	$85.692	$85.69	$85.70	$85.70
Purchase #6	$40.43	7.228%	$43.3523	$43.35	$43.35	$43.40
Purchase #7	$204.51	13.274%	$231.6567	$231.66	$231.65	$231.70
7 purchase totals =	$1,082.77		$1,180.0706	$1,180.07	$1,180.05	$1,180.30