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	$118.25	4.757%	$123.8752	$123.88	$123.90	$123.90
Purchase #2	$205.39	8.615%	$223.0843	$223.08	$223.10	$223.10
Purchase #3	$89.38	6.623%	$95.2996	$95.30	$95.30	$95.30
Purchase #4	$105.63	9.639%	$115.8117	$115.81	$115.80	$115.80
Purchase #5	$213.97	3.119%	$220.6437	$220.64	$220.65	$220.60
Purchase #6	$64.25	11.273%	$71.4929	$71.49	$71.50	$71.50
Purchase #7	$105.36	6.207%	$111.8997	$111.90	$111.90	$111.90
7 purchase totals =	$902.23		$962.1071	$962.10	$962.15	$962.10