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	$203.32	12.201%	$228.1271	$228.13	$228.15	$228.10
Purchase #2	$71.40	10.545%	$78.9291	$78.93	$78.95	$78.90
Purchase #3	$155.46	12.544%	$174.9609	$174.96	$174.95	$175.00
Purchase #4	$101.34	5.767%	$107.1843	$107.18	$107.20	$107.20
Purchase #5	$10.42	9.267%	$11.3856	$11.39	$11.40	$11.40
Purchase #6	$85.58	5.323%	$90.1354	$90.14	$90.15	$90.10
Purchase #7	$100.73	13.598%	$114.4273	$114.43	$114.45	$114.40
7 purchase totals =	$728.25		$805.1497	$805.16	$805.25	$805.10