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	$74.33	11.149%	$82.6171	$82.62	$82.60	$82.60
Purchase #2	$149.28	10.413%	$164.8245	$164.82	$164.80	$164.80
Purchase #3	$19.85	10.146%	$21.864	$21.86	$21.85	$21.90
Purchase #4	$133.45	13.687%	$151.7153	$151.72	$151.70	$151.70
Purchase #5	$139.42	13.378%	$158.0716	$158.07	$158.05	$158.10
Purchase #6	$166.64	10.413%	$183.9922	$183.99	$184.00	$184.00
Purchase #7	$249.74	3.521%	$258.5333	$258.53	$258.55	$258.50
7 purchase totals =	$932.71		$1,021.6180	$1,021.61	$1,021.55	$1,021.60