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	$196.62	4.477%	$205.4227	$205.42	$205.40	$205.40
Purchase #2	$244.67	4.357%	$255.3303	$255.33	$255.35	$255.30
Purchase #3	$111.77	10.406%	$123.4008	$123.40	$123.40	$123.40
Purchase #4	$233.64	5.833%	$247.2682	$247.27	$247.25	$247.30
Purchase #5	$136.90	12.161%	$153.5484	$153.55	$153.55	$153.50
Purchase #6	$137.54	7.281%	$147.5543	$147.55	$147.55	$147.60
Purchase #7	$32.33	6.336%	$34.3784	$34.38	$34.40	$34.40
7 purchase totals =	$1,093.47		$1,166.9031	$1,166.90	$1,166.90	$1,166.90