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	$193.48	7.805%	$208.5811	$208.58	$208.60	$208.60
Purchase #2	$77.44	12.175%	$86.8683	$86.87	$86.85	$86.90
Purchase #3	$67.97	7.145%	$72.8265	$72.83	$72.85	$72.80
Purchase #4	$50.25	7.785%	$54.162	$54.16	$54.15	$54.20
Purchase #5	$208.45	10.641%	$230.6312	$230.63	$230.65	$230.60
Purchase #6	$17.50	6.208%	$18.5864	$18.59	$18.60	$18.60
Purchase #7	$81.70	10.749%	$90.4819	$90.48	$90.50	$90.50
7 purchase totals =	$696.79		$762.1374	$762.14	$762.20	$762.20