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	$48.25	13.808%	$54.9124	$54.91	$54.90	$54.90
Purchase #2	$142.80	10.222%	$157.397	$157.40	$157.40	$157.40
Purchase #3	$17.69	9.305%	$19.3361	$19.34	$19.35	$19.30
Purchase #4	$182.36	4.178%	$189.979	$189.98	$190.00	$190.00
Purchase #5	$212.66	3.631%	$220.3817	$220.38	$220.40	$220.40
Purchase #6	$138.36	9.592%	$151.6315	$151.63	$151.65	$151.60
Purchase #7	$232.31	10.164%	$255.922	$255.92	$255.90	$255.90
7 purchase totals =	$974.43		$1,049.5597	$1,049.56	$1,049.60	$1,049.50