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	$114.56	10.580%	$126.6804	$126.68	$126.70	$126.70
Purchase #2	$44.81	10.672%	$49.5921	$49.59	$49.60	$49.60
Purchase #3	$99.96	11.599%	$111.5544	$111.55	$111.55	$111.60
Purchase #4	$164.99	11.277%	$183.5959	$183.60	$183.60	$183.60
Purchase #5	$221.47	9.558%	$242.6381	$242.64	$242.65	$242.60
Purchase #6	$184.69	6.637%	$196.9479	$196.95	$196.95	$196.90
Purchase #7	$177.58	10.585%	$196.3768	$196.38	$196.40	$196.40
7 purchase totals =	$1,008.06		$1,107.3856	$1,107.39	$1,107.45	$1,107.40