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	$109.78	3.519%	$113.6432	$113.64	$113.65	$113.60
Purchase #2	$158.70	4.630%	$166.0478	$166.05	$166.05	$166.00
Purchase #3	$53.30	10.709%	$59.0079	$59.01	$59.00	$59.00
Purchase #4	$51.73	5.550%	$54.601	$54.60	$54.60	$54.60
Purchase #5	$146.69	5.713%	$155.0704	$155.07	$155.05	$155.10
Purchase #6	$127.64	8.761%	$138.8225	$138.82	$138.80	$138.80
Purchase #7	$222.98	10.590%	$246.5936	$246.59	$246.60	$246.60
7 purchase totals =	$870.82		$933.7864	$933.78	$933.75	$933.70