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	$150.77	10.833%	$167.1029	$167.10	$167.10	$167.10
Purchase #2	$126.79	12.459%	$142.5868	$142.59	$142.60	$142.60
Purchase #3	$247.75	3.299%	$255.9233	$255.92	$255.90	$255.90
Purchase #4	$40.85	5.648%	$43.1572	$43.16	$43.15	$43.20
Purchase #5	$195.52	13.822%	$222.5448	$222.54	$222.55	$222.50
Purchase #6	$48.89	6.134%	$51.8889	$51.89	$51.90	$51.90
Purchase #7	$186.93	10.201%	$205.9987	$206.00	$206.00	$206.00
7 purchase totals =	$997.50		$1,089.2026	$1,089.20	$1,089.20	$1,089.20