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	$98.81	11.105%	$109.7829	$109.78	$109.80	$109.80
Purchase #2	$144.89	5.524%	$152.8937	$152.89	$152.90	$152.90
Purchase #3	$158.63	4.679%	$166.0523	$166.05	$166.05	$166.10
Purchase #4	$11.59	10.632%	$12.8222	$12.82	$12.80	$12.80
Purchase #5	$123.53	11.536%	$137.7804	$137.78	$137.80	$137.80
Purchase #6	$62.29	3.364%	$64.3854	$64.39	$64.40	$64.40
Purchase #7	$156.66	3.233%	$161.7248	$161.72	$161.70	$161.70
7 purchase totals =	$756.40		$805.4417	$805.43	$805.45	$805.50