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	$132.96	5.654%	$140.4776	$140.48	$140.50	$140.50
Purchase #2	$216.54	4.525%	$226.3384	$226.34	$226.35	$226.30
Purchase #3	$130.40	10.128%	$143.6069	$143.61	$143.60	$143.60
Purchase #4	$233.64	8.759%	$254.1045	$254.10	$254.10	$254.10
Purchase #5	$153.79	12.422%	$172.8938	$172.89	$172.90	$172.90
Purchase #6	$204.37	6.261%	$217.1656	$217.17	$217.15	$217.20
Purchase #7	$238.33	3.462%	$246.581	$246.58	$246.60	$246.60
7 purchase totals =	$1,310.03		$1,401.1678	$1,401.17	$1,401.20	$1,401.20