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	$151.77	10.734%	$168.061	$168.06	$168.05	$168.10
Purchase #2	$180.37	13.861%	$205.3711	$205.37	$205.35	$205.40
Purchase #3	$32.43	6.233%	$34.4514	$34.45	$34.45	$34.50
Purchase #4	$208.42	12.328%	$234.114	$234.11	$234.10	$234.10
Purchase #5	$35.67	9.249%	$38.9691	$38.97	$38.95	$39.00
Purchase #6	$179.69	3.400%	$185.7995	$185.80	$185.80	$185.80
Purchase #7	$244.78	13.623%	$278.1264	$278.13	$278.15	$278.10
7 purchase totals =	$1,033.13		$1,144.8925	$1,144.89	$1,144.85	$1,145.00