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	$234.38	7.352%	$251.6116	$251.61	$251.60	$251.60
Purchase #2	$148.85	13.484%	$168.9209	$168.92	$168.90	$168.90
Purchase #3	$130.92	4.187%	$136.4016	$136.40	$136.40	$136.40
Purchase #4	$52.52	3.291%	$54.2484	$54.25	$54.25	$54.20
Purchase #5	$174.27	10.792%	$193.0772	$193.08	$193.10	$193.10
Purchase #6	$117.27	8.462%	$127.1934	$127.19	$127.20	$127.20
Purchase #7	$93.45	12.492%	$105.1238	$105.12	$105.10	$105.10
7 purchase totals =	$951.66		$1,036.5769	$1,036.57	$1,036.55	$1,036.50