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	$100.59	8.189%	$108.8273	$108.83	$108.85	$108.80
Purchase #2	$68.96	3.622%	$71.4577	$71.46	$71.45	$71.50
Purchase #3	$219.31	10.308%	$241.9165	$241.92	$241.90	$241.90
Purchase #4	$120.46	11.689%	$134.5406	$134.54	$134.55	$134.50
Purchase #5	$213.40	12.418%	$239.9	$239.90	$239.90	$239.90
Purchase #6	$159.44	3.852%	$165.5816	$165.58	$165.60	$165.60
Purchase #7	$155.45	12.484%	$174.8564	$174.86	$174.85	$174.90
7 purchase totals =	$1,037.61		$1,137.0801	$1,137.09	$1,137.10	$1,137.10