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	$139.29	11.105%	$154.7582	$154.76	$154.75	$154.80
Purchase #2	$105.26	5.773%	$111.3367	$111.34	$111.35	$111.30
Purchase #3	$127.35	3.693%	$132.053	$132.05	$132.05	$132.10
Purchase #4	$101.47	10.252%	$111.8727	$111.87	$111.85	$111.90
Purchase #5	$122.74	7.121%	$131.4803	$131.48	$131.50	$131.50
Purchase #6	$147.46	11.357%	$164.207	$164.21	$164.20	$164.20
Purchase #7	$245.93	4.154%	$256.1459	$256.15	$256.15	$256.10
7 purchase totals =	$989.50		$1,061.8538	$1,061.86	$1,061.85	$1,061.90