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	$203.89	9.211%	$222.6703	$222.67	$222.65	$222.70
Purchase #2	$97.49	10.153%	$107.3882	$107.39	$107.40	$107.40
Purchase #3	$103.87	9.806%	$114.0555	$114.06	$114.05	$114.10
Purchase #4	$213.87	12.796%	$241.2368	$241.24	$241.25	$241.20
Purchase #5	$174.47	12.482%	$196.2473	$196.25	$196.25	$196.20
Purchase #6	$38.90	8.358%	$42.1513	$42.15	$42.15	$42.20
Purchase #7	$96.91	8.224%	$104.8799	$104.88	$104.90	$104.90
7 purchase totals =	$929.40		$1,028.6293	$1,028.64	$1,028.65	$1,028.70