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	$43.36	11.270%	$48.2467	$48.25	$48.25	$48.20
Purchase #2	$16.31	3.325%	$16.8523	$16.85	$16.85	$16.90
Purchase #3	$104.57	3.399%	$108.1243	$108.12	$108.10	$108.10
Purchase #4	$84.83	5.391%	$89.4032	$89.40	$89.40	$89.40
Purchase #5	$171.34	11.205%	$190.5386	$190.54	$190.55	$190.50
Purchase #6	$70.55	3.709%	$73.1667	$73.17	$73.15	$73.20
Purchase #7	$141.45	12.105%	$158.5725	$158.57	$158.55	$158.60
7 purchase totals =	$632.41		$684.9043	$684.90	$684.85	$684.90