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	$146.55	10.799%	$162.3759	$162.38	$162.40	$162.40
Purchase #2	$70.83	7.856%	$76.3944	$76.39	$76.40	$76.40
Purchase #3	$16.63	11.375%	$18.5217	$18.52	$18.50	$18.50
Purchase #4	$60.43	3.847%	$62.7547	$62.75	$62.75	$62.80
Purchase #5	$144.82	7.687%	$155.9523	$155.95	$155.95	$156.00
Purchase #6	$232.63	10.417%	$256.8631	$256.86	$256.85	$256.90
Purchase #7	$154.63	12.481%	$173.9294	$173.93	$173.95	$173.90
7 purchase totals =	$826.52		$906.7915	$906.78	$906.80	$906.90