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	$72.98	13.561%	$82.8768	$82.88	$82.90	$82.90
Purchase #2	$138.51	3.577%	$143.4645	$143.46	$143.45	$143.50
Purchase #3	$157.86	11.351%	$175.7787	$175.78	$175.80	$175.80
Purchase #4	$75.83	3.428%	$78.4295	$78.43	$78.45	$78.40
Purchase #5	$39.67	10.819%	$43.9619	$43.96	$43.95	$44.00
Purchase #6	$249.93	11.177%	$277.8647	$277.86	$277.85	$277.90
Purchase #7	$66.75	11.786%	$74.6172	$74.62	$74.60	$74.60
7 purchase totals =	$801.53		$876.9933	$876.99	$877.00	$877.10