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	$242.65	3.371%	$250.8297	$250.83	$250.85	$250.80
Purchase #2	$19.92	3.573%	$20.6317	$20.63	$20.65	$20.60
Purchase #3	$80.78	7.491%	$86.8312	$86.83	$86.85	$86.80
Purchase #4	$246.81	9.618%	$270.5482	$270.55	$270.55	$270.50
Purchase #5	$104.29	7.124%	$111.7196	$111.72	$111.70	$111.70
Purchase #6	$158.76	11.249%	$176.6189	$176.62	$176.60	$176.60
Purchase #7	$21.87	4.720%	$22.9023	$22.90	$22.90	$22.90
7 purchase totals =	$875.08		$940.0816	$940.08	$940.10	$939.90