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	$128.25	11.188%	$142.5986	$142.60	$142.60	$142.60
Purchase #2	$185.81	4.864%	$194.8478	$194.85	$194.85	$194.80
Purchase #3	$106.99	4.112%	$111.3894	$111.39	$111.40	$111.40
Purchase #4	$40.98	8.644%	$44.5223	$44.52	$44.50	$44.50
Purchase #5	$174.70	13.855%	$198.9047	$198.90	$198.90	$198.90
Purchase #6	$19.62	11.771%	$21.9295	$21.93	$21.95	$21.90
Purchase #7	$50.85	9.129%	$55.4921	$55.49	$55.50	$55.50
7 purchase totals =	$707.20		$769.6844	$769.68	$769.70	$769.60