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	$182.32	12.182%	$204.5302	$204.53	$204.55	$204.50
Purchase #2	$241.39	7.149%	$258.647	$258.65	$258.65	$258.60
Purchase #3	$118.59	3.737%	$123.0217	$123.02	$123.00	$123.00
Purchase #4	$71.91	8.485%	$78.0116	$78.01	$78.00	$78.00
Purchase #5	$250.42	13.448%	$284.0965	$284.10	$284.10	$284.10
Purchase #6	$137.53	10.176%	$151.5251	$151.53	$151.55	$151.50
Purchase #7	$42.44	5.584%	$44.8098	$44.81	$44.80	$44.80
7 purchase totals =	$1,044.60		$1,144.6419	$1,144.65	$1,144.65	$1,144.50