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	$248.46	5.722%	$262.6769	$262.68	$262.70	$262.70
Purchase #2	$167.85	11.620%	$187.3542	$187.35	$187.35	$187.40
Purchase #3	$25.83	9.458%	$28.273	$28.27	$28.25	$28.30
Purchase #4	$72.25	6.111%	$76.6652	$76.67	$76.65	$76.70
Purchase #5	$154.99	8.826%	$168.6694	$168.67	$168.65	$168.70
Purchase #6	$176.74	5.212%	$185.9517	$185.95	$185.95	$186.00
Purchase #7	$107.86	3.239%	$111.3536	$111.35	$111.35	$111.40
7 purchase totals =	$953.98		$1,020.9440	$1,020.94	$1,020.90	$1,021.20