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	$128.82	11.480%	$143.6085	$143.61	$143.60	$143.60
Purchase #2	$40.94	10.246%	$45.1347	$45.13	$45.15	$45.10
Purchase #3	$152.84	4.134%	$159.1584	$159.16	$159.15	$159.20
Purchase #4	$154.37	8.849%	$168.0302	$168.03	$168.05	$168.00
Purchase #5	$224.45	11.344%	$249.9116	$249.91	$249.90	$249.90
Purchase #6	$212.73	6.685%	$226.951	$226.95	$226.95	$227.00
Purchase #7	$40.92	11.642%	$45.6839	$45.68	$45.70	$45.70
7 purchase totals =	$955.07		$1,038.4783	$1,038.47	$1,038.50	$1,038.50