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	$57.64	8.632%	$62.6155	$62.62	$62.60	$62.60
Purchase #2	$120.93	12.762%	$136.3631	$136.36	$136.35	$136.40
Purchase #3	$210.78	8.556%	$228.8143	$228.81	$228.80	$228.80
Purchase #4	$107.71	3.292%	$111.2558	$111.26	$111.25	$111.30
Purchase #5	$148.47	12.799%	$167.4727	$167.47	$167.45	$167.50
Purchase #6	$119.90	6.543%	$127.7451	$127.75	$127.75	$127.70
Purchase #7	$90.27	9.470%	$98.8186	$98.82	$98.80	$98.80
7 purchase totals =	$855.70		$933.0851	$933.09	$933.00	$933.10