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	$213.70	9.208%	$233.3775	$233.38	$233.40	$233.40
Purchase #2	$246.83	12.342%	$277.2938	$277.29	$277.30	$277.30
Purchase #3	$160.35	3.438%	$165.8628	$165.86	$165.85	$165.90
Purchase #4	$215.98	10.569%	$238.8069	$238.81	$238.80	$238.80
Purchase #5	$241.92	12.307%	$271.6931	$271.69	$271.70	$271.70
Purchase #6	$142.54	6.446%	$151.7281	$151.73	$151.75	$151.70
Purchase #7	$37.60	13.369%	$42.6267	$42.63	$42.65	$42.60
7 purchase totals =	$1,258.92		$1,381.3889	$1,381.39	$1,381.45	$1,381.40