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	$147.79	12.642%	$166.4736	$166.47	$166.45	$166.50
Purchase #2	$167.92	9.353%	$183.6256	$183.63	$183.65	$183.60
Purchase #3	$75.52	4.406%	$78.8474	$78.85	$78.85	$78.80
Purchase #4	$84.95	3.512%	$87.9334	$87.93	$87.95	$87.90
Purchase #5	$95.72	4.854%	$100.3662	$100.37	$100.35	$100.40
Purchase #6	$128.45	10.854%	$142.392	$142.39	$142.40	$142.40
Purchase #7	$97.98	6.775%	$104.6181	$104.62	$104.60	$104.60
7 purchase totals =	$798.33		$864.2563	$864.26	$864.25	$864.20