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	$138.78	11.768%	$155.1116	$155.11	$155.10	$155.10
Purchase #2	$149.86	3.742%	$155.4678	$155.47	$155.45	$155.50
Purchase #3	$246.42	4.381%	$257.2157	$257.22	$257.20	$257.20
Purchase #4	$42.50	3.418%	$43.9527	$43.95	$43.95	$44.00
Purchase #5	$171.85	4.510%	$179.6004	$179.60	$179.60	$179.60
Purchase #6	$152.94	10.735%	$169.3581	$169.36	$169.35	$169.40
Purchase #7	$49.26	5.734%	$52.0846	$52.08	$52.10	$52.10
7 purchase totals =	$951.61		$1,012.7909	$1,012.79	$1,012.75	$1,012.90