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	$9.94	10.401%	$10.9739	$10.97	$10.95	$11.00
Purchase #2	$8.25	8.396%	$8.9427	$8.94	$8.95	$8.90
Purchase #3	$5.91	10.318%	$6.5198	$6.52	$6.50	$6.50
Purchase #4	$98.46	13.569%	$111.82	$111.82	$111.80	$111.80
Purchase #5	$118.82	3.561%	$123.0512	$123.05	$123.05	$123.10
Purchase #6	$54.81	3.230%	$56.5804	$56.58	$56.60	$56.60
Purchase #7	$202.53	4.121%	$210.8763	$210.88	$210.90	$210.90
7 purchase totals =	$498.72		$528.7643	$528.76	$528.75	$528.80