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	$230.71	10.577%	$255.1122	$255.11	$255.10	$255.10
Purchase #2	$230.64	12.716%	$259.9682	$259.97	$259.95	$260.00
Purchase #3	$155.73	12.401%	$175.0421	$175.04	$175.05	$175.00
Purchase #4	$172.53	4.215%	$179.8021	$179.80	$179.80	$179.80
Purchase #5	$55.89	13.684%	$63.538	$63.54	$63.55	$63.50
Purchase #6	$96.25	7.573%	$103.539	$103.54	$103.55	$103.50
Purchase #7	$62.73	3.589%	$64.9814	$64.98	$65.00	$65.00
7 purchase totals =	$1,004.48		$1,101.9830	$1,101.98	$1,102.00	$1,101.90