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	$226.58	6.760%	$241.8968	$241.90	$241.90	$241.90
Purchase #2	$143.87	11.869%	$160.9459	$160.95	$160.95	$160.90
Purchase #3	$173.82	5.832%	$183.9572	$183.96	$183.95	$184.00
Purchase #4	$71.54	9.513%	$78.3456	$78.35	$78.35	$78.30
Purchase #5	$127.59	5.122%	$134.1252	$134.13	$134.15	$134.10
Purchase #6	$79.82	6.602%	$85.0897	$85.09	$85.10	$85.10
Purchase #7	$170.86	3.414%	$176.6932	$176.69	$176.70	$176.70
7 purchase totals =	$994.08		$1,061.0536	$1,061.07	$1,061.10	$1,061.00