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	$241.97	3.773%	$251.0995	$251.10	$251.10	$251.10
Purchase #2	$114.54	13.498%	$130.0006	$130.00	$130.00	$130.00
Purchase #3	$128.25	3.636%	$132.9132	$132.91	$132.90	$132.90
Purchase #4	$77.96	6.161%	$82.7631	$82.76	$82.75	$82.80
Purchase #5	$138.60	6.838%	$148.0775	$148.08	$148.10	$148.10
Purchase #6	$155.59	11.565%	$173.584	$173.58	$173.60	$173.60
Purchase #7	$132.96	7.260%	$142.6129	$142.61	$142.60	$142.60
7 purchase totals =	$989.87		$1,061.0508	$1,061.04	$1,061.05	$1,061.10