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	$138.87	11.249%	$154.4915	$154.49	$154.50	$154.50
Purchase #2	$53.89	3.733%	$55.9017	$55.90	$55.90	$55.90
Purchase #3	$148.25	4.517%	$154.9465	$154.95	$154.95	$154.90
Purchase #4	$83.34	13.736%	$94.7876	$94.79	$94.80	$94.80
Purchase #5	$129.27	9.853%	$142.007	$142.01	$142.00	$142.00
Purchase #6	$229.89	7.738%	$247.6789	$247.68	$247.70	$247.70
Purchase #7	$155.42	5.609%	$164.1375	$164.14	$164.15	$164.10
7 purchase totals =	$938.93		$1,013.9507	$1,013.96	$1,014.00	$1,013.90