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	$246.89	13.341%	$279.8276	$279.83	$279.85	$279.80
Purchase #2	$213.38	6.656%	$227.5826	$227.58	$227.60	$227.60
Purchase #3	$199.93	10.579%	$221.0806	$221.08	$221.10	$221.10
Purchase #4	$182.26	12.755%	$205.5073	$205.51	$205.50	$205.50
Purchase #5	$152.71	10.382%	$168.5644	$168.56	$168.55	$168.60
Purchase #6	$235.41	4.367%	$245.6904	$245.69	$245.70	$245.70
Purchase #7	$106.25	12.138%	$119.1466	$119.15	$119.15	$119.10
7 purchase totals =	$1,336.83		$1,467.3995	$1,467.40	$1,467.45	$1,467.40