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	$179.55	5.320%	$189.1021	$189.10	$189.10	$189.10
Purchase #2	$168.25	3.346%	$173.8796	$173.88	$173.90	$173.90
Purchase #3	$81.48	11.507%	$90.8559	$90.86	$90.85	$90.90
Purchase #4	$95.50	4.571%	$99.8653	$99.87	$99.85	$99.90
Purchase #5	$52.91	6.669%	$56.4386	$56.44	$56.45	$56.40
Purchase #6	$121.47	4.119%	$126.4733	$126.47	$126.45	$126.50
Purchase #7	$151.67	11.263%	$168.7526	$168.75	$168.75	$168.80
7 purchase totals =	$850.83		$905.3674	$905.37	$905.35	$905.50