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	$236.86	11.869%	$264.9729	$264.97	$264.95	$265.00
Purchase #2	$66.46	9.642%	$72.8681	$72.87	$72.85	$72.90
Purchase #3	$193.30	5.858%	$204.6235	$204.62	$204.60	$204.60
Purchase #4	$41.92	6.687%	$44.7232	$44.72	$44.70	$44.70
Purchase #5	$41.39	3.782%	$42.9554	$42.96	$42.95	$43.00
Purchase #6	$228.33	4.380%	$238.3309	$238.33	$238.35	$238.30
Purchase #7	$39.51	6.564%	$42.1034	$42.10	$42.10	$42.10
7 purchase totals =	$847.77		$910.5774	$910.57	$910.50	$910.60