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	$54.97	13.847%	$62.5817	$62.58	$62.60	$62.60
Purchase #2	$50.85	6.291%	$54.049	$54.05	$54.05	$54.00
Purchase #3	$133.26	5.147%	$140.1189	$140.12	$140.10	$140.10
Purchase #4	$118.29	13.718%	$134.517	$134.52	$134.50	$134.50
Purchase #5	$117.69	12.853%	$132.8167	$132.82	$132.80	$132.80
Purchase #6	$180.64	7.319%	$193.861	$193.86	$193.85	$193.90
Purchase #7	$99.89	13.706%	$113.5809	$113.58	$113.60	$113.60
7 purchase totals =	$755.59		$831.5252	$831.53	$831.50	$831.50