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	$40.41	7.648%	$43.5006	$43.50	$43.50	$43.50
Purchase #2	$125.78	13.431%	$142.6735	$142.67	$142.65	$142.70
Purchase #3	$41.51	5.616%	$43.8412	$43.84	$43.85	$43.80
Purchase #4	$244.28	10.507%	$269.9465	$269.95	$269.95	$269.90
Purchase #5	$113.83	3.575%	$117.8994	$117.90	$117.90	$117.90
Purchase #6	$234.40	12.225%	$263.0554	$263.06	$263.05	$263.10
Purchase #7	$26.34	4.867%	$27.622	$27.62	$27.60	$27.60
7 purchase totals =	$826.55		$908.5386	$908.54	$908.50	$908.50