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	$162.34	3.766%	$168.4537	$168.45	$168.45	$168.50
Purchase #2	$142.31	9.659%	$156.0557	$156.06	$156.05	$156.10
Purchase #3	$176.87	12.852%	$199.6013	$199.60	$199.60	$199.60
Purchase #4	$50.98	9.452%	$55.7986	$55.80	$55.80	$55.80
Purchase #5	$101.64	10.803%	$112.6202	$112.62	$112.60	$112.60
Purchase #6	$209.81	11.457%	$233.8479	$233.85	$233.85	$233.80
Purchase #7	$226.61	4.328%	$236.4177	$236.42	$236.40	$236.40
7 purchase totals =	$1,070.56		$1,162.7951	$1,162.80	$1,162.75	$1,162.80