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	$150.79	7.441%	$162.0103	$162.01	$162.00	$162.00
Purchase #2	$53.86	12.687%	$60.6932	$60.69	$60.70	$60.70
Purchase #3	$155.28	7.186%	$166.4384	$166.44	$166.45	$166.40
Purchase #4	$81.82	10.123%	$90.1026	$90.10	$90.10	$90.10
Purchase #5	$18.94	13.618%	$21.5192	$21.52	$21.50	$21.50
Purchase #6	$66.66	5.672%	$70.441	$70.44	$70.45	$70.40
Purchase #7	$125.69	13.318%	$142.4294	$142.43	$142.45	$142.40
7 purchase totals =	$653.04		$713.6341	$713.63	$713.65	$713.50