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	$101.66	10.304%	$112.135	$112.14	$112.15	$112.10
Purchase #2	$10.94	13.299%	$12.3949	$12.39	$12.40	$12.40
Purchase #3	$176.94	13.360%	$200.5792	$200.58	$200.60	$200.60
Purchase #4	$100.73	10.727%	$111.5353	$111.54	$111.55	$111.50
Purchase #5	$117.85	5.194%	$123.9711	$123.97	$123.95	$124.00
Purchase #6	$126.41	5.551%	$133.427	$133.43	$133.45	$133.40
Purchase #7	$159.44	10.416%	$176.0473	$176.05	$176.05	$176.00
7 purchase totals =	$793.97		$870.0898	$870.10	$870.15	$870.00