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	$57.47	9.408%	$62.8768	$62.88	$62.90	$62.90
Purchase #2	$13.49	7.193%	$14.4603	$14.46	$14.45	$14.50
Purchase #3	$113.57	9.112%	$123.9185	$123.92	$123.90	$123.90
Purchase #4	$17.39	9.810%	$19.096	$19.10	$19.10	$19.10
Purchase #5	$41.89	4.626%	$43.8278	$43.83	$43.85	$43.80
Purchase #6	$159.97	7.537%	$172.0269	$172.03	$172.05	$172.00
Purchase #7	$10.78	3.309%	$11.1367	$11.14	$11.15	$11.10
7 purchase totals =	$414.56		$447.3430	$447.36	$447.40	$447.30