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	$141.85	9.308%	$155.0534	$155.05	$155.05	$155.10
Purchase #2	$208.83	4.681%	$218.6053	$218.61	$218.60	$218.60
Purchase #3	$77.91	5.116%	$81.8959	$81.90	$81.90	$81.90
Purchase #4	$106.98	9.438%	$117.0768	$117.08	$117.10	$117.10
Purchase #5	$139.50	12.463%	$156.8859	$156.89	$156.90	$156.90
Purchase #6	$163.58	5.502%	$172.5802	$172.58	$172.60	$172.60
Purchase #7	$159.98	11.431%	$178.2673	$178.27	$178.25	$178.30
7 purchase totals =	$998.63		$1,080.3648	$1,080.38	$1,080.40	$1,080.50