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	$93.76	8.871%	$102.0774	$102.08	$102.10	$102.10
Purchase #2	$209.73	8.674%	$227.922	$227.92	$227.90	$227.90
Purchase #3	$32.62	5.601%	$34.447	$34.45	$34.45	$34.40
Purchase #4	$142.80	9.681%	$156.6245	$156.62	$156.60	$156.60
Purchase #5	$116.47	13.423%	$132.1038	$132.10	$132.10	$132.10
Purchase #6	$137.62	13.375%	$156.0267	$156.03	$156.05	$156.00
Purchase #7	$103.40	8.195%	$111.8736	$111.87	$111.85	$111.90
7 purchase totals =	$836.40		$921.0750	$921.07	$921.05	$921.00