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	$63.69	5.390%	$67.1229	$67.12	$67.10	$67.10
Purchase #2	$126.60	3.551%	$131.0956	$131.10	$131.10	$131.10
Purchase #3	$141.76	12.516%	$159.5027	$159.50	$159.50	$159.50
Purchase #4	$20.83	12.795%	$23.4952	$23.50	$23.50	$23.50
Purchase #5	$169.75	4.677%	$177.6892	$177.69	$177.70	$177.70
Purchase #6	$238.99	10.149%	$263.2451	$263.25	$263.25	$263.20
Purchase #7	$142.84	9.554%	$156.4869	$156.49	$156.50	$156.50
7 purchase totals =	$904.46		$978.6376	$978.65	$978.65	$978.60