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	$102.90	8.658%	$111.8091	$111.81	$111.80	$111.80
Purchase #2	$176.70	11.259%	$196.5947	$196.59	$196.60	$196.60
Purchase #3	$196.39	4.174%	$204.5873	$204.59	$204.60	$204.60
Purchase #4	$182.59	10.859%	$202.4174	$202.42	$202.40	$202.40
Purchase #5	$146.31	6.553%	$155.8977	$155.90	$155.90	$155.90
Purchase #6	$100.80	12.663%	$113.5643	$113.56	$113.55	$113.60
Purchase #7	$91.62	5.685%	$96.8286	$96.83	$96.85	$96.80
7 purchase totals =	$997.31		$1,081.6991	$1,081.70	$1,081.70	$1,081.70