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	$225.25	10.710%	$249.3743	$249.37	$249.35	$249.40
Purchase #2	$224.85	4.489%	$234.9435	$234.94	$234.95	$234.90
Purchase #3	$89.35	10.232%	$98.4923	$98.49	$98.50	$98.50
Purchase #4	$120.81	8.422%	$130.9846	$130.98	$131.00	$131.00
Purchase #5	$124.68	7.193%	$133.6482	$133.65	$133.65	$133.60
Purchase #6	$156.70	12.424%	$176.1684	$176.17	$176.15	$176.20
Purchase #7	$111.90	13.572%	$127.0871	$127.09	$127.10	$127.10
7 purchase totals =	$1,053.54		$1,150.6984	$1,150.69	$1,150.70	$1,150.70