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	$63.42	12.461%	$71.3228	$71.32	$71.30	$71.30
Purchase #2	$150.77	3.695%	$156.341	$156.34	$156.35	$156.30
Purchase #3	$67.64	5.863%	$71.6057	$71.61	$71.60	$71.60
Purchase #4	$202.30	3.260%	$208.895	$208.90	$208.90	$208.90
Purchase #5	$106.50	9.462%	$116.577	$116.58	$116.60	$116.60
Purchase #6	$155.85	5.246%	$164.0259	$164.03	$164.05	$164.00
Purchase #7	$64.59	4.649%	$67.5928	$67.59	$67.60	$67.60
7 purchase totals =	$811.07		$856.3602	$856.37	$856.40	$856.30