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	$122.61	4.631%	$128.2881	$128.29	$128.30	$128.30
Purchase #2	$22.70	5.125%	$23.8634	$23.86	$23.85	$23.90
Purchase #3	$215.73	11.633%	$240.8259	$240.83	$240.85	$240.80
Purchase #4	$152.60	13.756%	$173.5917	$173.59	$173.60	$173.60
Purchase #5	$59.38	11.266%	$66.0698	$66.07	$66.05	$66.10
Purchase #6	$205.50	4.202%	$214.1351	$214.14	$214.15	$214.10
Purchase #7	$74.42	5.147%	$78.2504	$78.25	$78.25	$78.30
7 purchase totals =	$852.94		$925.0244	$925.03	$925.05	$925.10