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	$234.41	9.153%	$255.8655	$255.87	$255.85	$255.90
Purchase #2	$48.37	6.150%	$51.3448	$51.34	$51.35	$51.30
Purchase #3	$171.36	11.213%	$190.5746	$190.57	$190.55	$190.60
Purchase #4	$32.95	6.560%	$35.1115	$35.11	$35.10	$35.10
Purchase #5	$155.70	4.668%	$162.9681	$162.97	$162.95	$163.00
Purchase #6	$183.40	4.111%	$190.9396	$190.94	$190.95	$190.90
Purchase #7	$113.51	4.491%	$118.6077	$118.61	$118.60	$118.60
7 purchase totals =	$939.70		$1,005.4118	$1,005.41	$1,005.35	$1,005.40