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	$20.79	11.574%	$23.1962	$23.20	$23.20	$23.20
Purchase #2	$224.66	4.462%	$234.6843	$234.68	$234.70	$234.70
Purchase #3	$38.81	4.203%	$40.4412	$40.44	$40.45	$40.40
Purchase #4	$86.51	3.556%	$89.5863	$89.59	$89.60	$89.60
Purchase #5	$100.81	13.781%	$114.7026	$114.70	$114.70	$114.70
Purchase #6	$141.90	7.188%	$152.0998	$152.10	$152.10	$152.10
Purchase #7	$127.75	3.796%	$132.5994	$132.60	$132.60	$132.60
7 purchase totals =	$741.23		$787.3098	$787.31	$787.35	$787.30