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	$177.85	12.746%	$200.5188	$200.52	$200.50	$200.50
Purchase #2	$107.37	3.646%	$111.2847	$111.28	$111.30	$111.30
Purchase #3	$164.40	8.604%	$178.545	$178.55	$178.55	$178.50
Purchase #4	$59.49	8.208%	$64.3729	$64.37	$64.35	$64.40
Purchase #5	$180.33	13.454%	$204.5916	$204.59	$204.60	$204.60
Purchase #6	$84.70	12.768%	$95.5145	$95.51	$95.50	$95.50
Purchase #7	$102.56	8.298%	$111.0704	$111.07	$111.05	$111.10
7 purchase totals =	$876.70		$965.8979	$965.89	$965.85	$965.90