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	$32.40	7.577%	$34.8549	$34.85	$34.85	$34.90
Purchase #2	$142.32	9.383%	$155.6739	$155.67	$155.65	$155.70
Purchase #3	$11.99	12.560%	$13.4959	$13.50	$13.50	$13.50
Purchase #4	$98.86	5.123%	$103.9246	$103.92	$103.90	$103.90
Purchase #5	$206.95	3.271%	$213.7193	$213.72	$213.70	$213.70
Purchase #6	$43.32	5.178%	$45.5631	$45.56	$45.55	$45.60
Purchase #7	$187.71	9.449%	$205.4467	$205.45	$205.45	$205.40
7 purchase totals =	$723.55		$772.6784	$772.67	$772.60	$772.70