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	$158.36	6.753%	$169.0541	$169.05	$169.05	$169.10
Purchase #2	$56.34	5.412%	$59.3891	$59.39	$59.40	$59.40
Purchase #3	$107.49	3.658%	$111.422	$111.42	$111.40	$111.40
Purchase #4	$144.83	13.702%	$164.6746	$164.67	$164.65	$164.70
Purchase #5	$11.78	4.742%	$12.3386	$12.34	$12.35	$12.30
Purchase #6	$167.87	11.457%	$187.1029	$187.10	$187.10	$187.10
Purchase #7	$143.41	12.864%	$161.8583	$161.86	$161.85	$161.90
7 purchase totals =	$790.08		$865.8396	$865.83	$865.80	$865.90