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	$164.49	3.248%	$169.8326	$169.83	$169.85	$169.80
Purchase #2	$198.64	13.302%	$225.0631	$225.06	$225.05	$225.10
Purchase #3	$49.75	7.607%	$53.5345	$53.53	$53.55	$53.50
Purchase #4	$229.38	11.245%	$255.1738	$255.17	$255.15	$255.20
Purchase #5	$154.58	4.655%	$161.7757	$161.78	$161.80	$161.80
Purchase #6	$101.60	9.245%	$110.9929	$110.99	$111.00	$111.00
Purchase #7	$123.45	4.477%	$128.9769	$128.98	$129.00	$129.00
7 purchase totals =	$1,021.89		$1,105.3495	$1,105.34	$1,105.40	$1,105.40