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	$117.80	5.163%	$123.882	$123.88	$123.90	$123.90
Purchase #2	$226.83	5.325%	$238.9087	$238.91	$238.90	$238.90
Purchase #3	$210.63	4.369%	$219.8324	$219.83	$219.85	$219.80
Purchase #4	$25.42	10.403%	$28.0644	$28.06	$28.05	$28.10
Purchase #5	$172.52	6.358%	$183.4888	$183.49	$183.50	$183.50
Purchase #6	$205.47	7.190%	$220.2433	$220.24	$220.25	$220.20
Purchase #7	$57.95	8.617%	$62.9436	$62.94	$62.95	$62.90
7 purchase totals =	$1,016.62		$1,077.3632	$1,077.35	$1,077.40	$1,077.30