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	$134.79	10.153%	$148.4752	$148.48	$148.50	$148.50
Purchase #2	$10.75	6.410%	$11.4391	$11.44	$11.45	$11.40
Purchase #3	$153.48	12.392%	$172.4992	$172.50	$172.50	$172.50
Purchase #4	$132.38	13.670%	$150.4763	$150.48	$150.50	$150.50
Purchase #5	$194.29	12.528%	$218.6307	$218.63	$218.65	$218.60
Purchase #6	$85.42	10.794%	$94.6402	$94.64	$94.65	$94.60
Purchase #7	$141.41	3.505%	$146.3664	$146.37	$146.35	$146.40
7 purchase totals =	$852.52		$942.5271	$942.54	$942.60	$942.50