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	$150.34	11.826%	$168.1192	$168.12	$168.10	$168.10
Purchase #2	$12.86	5.109%	$13.517	$13.52	$13.50	$13.50
Purchase #3	$55.99	12.423%	$62.9456	$62.95	$62.95	$62.90
Purchase #4	$192.25	12.660%	$216.5889	$216.59	$216.60	$216.60
Purchase #5	$136.71	3.839%	$141.9583	$141.96	$141.95	$142.00
Purchase #6	$133.63	8.196%	$144.5823	$144.58	$144.60	$144.60
Purchase #7	$187.45	3.659%	$194.3088	$194.31	$194.30	$194.30
7 purchase totals =	$869.23		$942.0201	$942.03	$942.00	$942.00