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	$211.78	13.446%	$240.2559	$240.26	$240.25	$240.30
Purchase #2	$39.70	4.262%	$41.392	$41.39	$41.40	$41.40
Purchase #3	$5.54	6.509%	$5.9006	$5.90	$5.90	$5.90
Purchase #4	$41.26	3.274%	$42.6109	$42.61	$42.60	$42.60
Purchase #5	$132.52	11.209%	$147.3742	$147.37	$147.35	$147.40
Purchase #6	$57.37	13.413%	$65.065	$65.07	$65.05	$65.10
Purchase #7	$249.28	9.352%	$272.5927	$272.59	$272.60	$272.60
7 purchase totals =	$737.45		$815.1913	$815.19	$815.15	$815.30