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	$226.69	7.145%	$242.887	$242.89	$242.90	$242.90
Purchase #2	$224.58	7.855%	$242.2208	$242.22	$242.20	$242.20
Purchase #3	$50.59	7.798%	$54.535	$54.54	$54.55	$54.50
Purchase #4	$90.67	10.352%	$100.0562	$100.06	$100.05	$100.10
Purchase #5	$224.92	5.222%	$236.6653	$236.67	$236.65	$236.70
Purchase #6	$146.79	13.496%	$166.6008	$166.60	$166.60	$166.60
Purchase #7	$19.62	8.409%	$21.2698	$21.27	$21.25	$21.30
7 purchase totals =	$983.86		$1,064.2349	$1,064.25	$1,064.20	$1,064.30