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	$78.40	9.723%	$86.0228	$86.02	$86.00	$86.00
Purchase #2	$43.42	11.748%	$48.521	$48.52	$48.50	$48.50
Purchase #3	$171.26	4.648%	$179.2202	$179.22	$179.20	$179.20
Purchase #4	$42.32	10.484%	$46.7568	$46.76	$46.75	$46.80
Purchase #5	$174.90	3.739%	$181.4395	$181.44	$181.45	$181.40
Purchase #6	$29.59	13.378%	$33.5486	$33.55	$33.55	$33.50
Purchase #7	$32.80	6.105%	$34.8024	$34.80	$34.80	$34.80
7 purchase totals =	$572.69		$610.3113	$610.31	$610.25	$610.20