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	$101.54	9.713%	$111.4026	$111.40	$111.40	$111.40
Purchase #2	$217.42	5.624%	$229.6477	$229.65	$229.65	$229.60
Purchase #3	$14.58	5.518%	$15.3845	$15.38	$15.40	$15.40
Purchase #4	$132.26	9.165%	$144.3816	$144.38	$144.40	$144.40
Purchase #5	$199.87	6.557%	$212.9755	$212.98	$213.00	$213.00
Purchase #6	$83.72	8.289%	$90.6596	$90.66	$90.65	$90.70
Purchase #7	$129.72	9.448%	$141.9759	$141.98	$142.00	$142.00
7 purchase totals =	$879.11		$946.4274	$946.43	$946.50	$946.50