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	$103.75	9.484%	$113.5897	$113.59	$113.60	$113.60
Purchase #2	$166.29	8.711%	$180.7755	$180.78	$180.80	$180.80
Purchase #3	$86.44	13.202%	$97.8518	$97.85	$97.85	$97.90
Purchase #4	$10.78	6.246%	$11.4533	$11.45	$11.45	$11.50
Purchase #5	$100.86	4.610%	$105.5096	$105.51	$105.50	$105.50
Purchase #6	$38.44	11.827%	$42.9863	$42.99	$43.00	$43.00
Purchase #7	$191.96	11.457%	$213.9529	$213.95	$213.95	$214.00
7 purchase totals =	$698.52		$766.1191	$766.12	$766.15	$766.30