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	$205.42	8.471%	$222.8211	$222.82	$222.80	$222.80
Purchase #2	$55.94	3.418%	$57.852	$57.85	$57.85	$57.90
Purchase #3	$126.92	3.670%	$131.578	$131.58	$131.60	$131.60
Purchase #4	$38.45	11.715%	$42.9544	$42.95	$42.95	$43.00
Purchase #5	$35.79	6.533%	$38.1282	$38.13	$38.15	$38.10
Purchase #6	$37.91	12.579%	$42.6787	$42.68	$42.70	$42.70
Purchase #7	$160.34	10.603%	$177.3409	$177.34	$177.35	$177.30
7 purchase totals =	$660.77		$713.3533	$713.35	$713.40	$713.40