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	$147.31	11.664%	$164.4922	$164.49	$164.50	$164.50
Purchase #2	$141.76	12.810%	$159.9195	$159.92	$159.90	$159.90
Purchase #3	$78.89	11.669%	$88.0957	$88.10	$88.10	$88.10
Purchase #4	$214.45	5.829%	$226.9503	$226.95	$226.95	$227.00
Purchase #5	$163.98	13.145%	$185.5352	$185.54	$185.55	$185.50
Purchase #6	$95.79	8.633%	$104.0596	$104.06	$104.05	$104.10
Purchase #7	$32.86	4.741%	$34.4179	$34.42	$34.40	$34.40
7 purchase totals =	$875.04		$963.4704	$963.48	$963.45	$963.50