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	$199.47	13.201%	$225.802	$225.80	$225.80	$225.80
Purchase #2	$178.64	9.699%	$195.9663	$195.97	$195.95	$196.00
Purchase #3	$234.62	10.712%	$259.7525	$259.75	$259.75	$259.80
Purchase #4	$105.33	6.575%	$112.2554	$112.26	$112.25	$112.30
Purchase #5	$105.32	12.556%	$118.544	$118.54	$118.55	$118.50
Purchase #6	$102.85	8.737%	$111.836	$111.84	$111.85	$111.80
Purchase #7	$229.88	3.790%	$238.5925	$238.59	$238.60	$238.60
7 purchase totals =	$1,156.11		$1,262.7487	$1,262.75	$1,262.75	$1,262.80