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	$204.37	3.656%	$211.8418	$211.84	$211.85	$211.80
Purchase #2	$102.89	11.589%	$114.8139	$114.81	$114.80	$114.80
Purchase #3	$69.85	12.138%	$78.3284	$78.33	$78.35	$78.30
Purchase #4	$213.43	4.416%	$222.8551	$222.86	$222.85	$222.90
Purchase #5	$237.38	7.164%	$254.3859	$254.39	$254.40	$254.40
Purchase #6	$106.79	4.673%	$111.7803	$111.78	$111.80	$111.80
Purchase #7	$230.95	12.615%	$260.0843	$260.08	$260.10	$260.10
7 purchase totals =	$1,165.66		$1,254.0897	$1,254.09	$1,254.15	$1,254.10