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	$212.98	12.132%	$238.8187	$238.82	$238.80	$238.80
Purchase #2	$17.93	3.398%	$18.5393	$18.54	$18.55	$18.50
Purchase #3	$34.90	13.689%	$39.6775	$39.68	$39.70	$39.70
Purchase #4	$146.75	4.597%	$153.4961	$153.50	$153.50	$153.50
Purchase #5	$116.55	7.509%	$125.3017	$125.30	$125.30	$125.30
Purchase #6	$103.31	9.243%	$112.8589	$112.86	$112.85	$112.90
Purchase #7	$142.45	12.740%	$160.5981	$160.60	$160.60	$160.60
7 purchase totals =	$774.87		$849.2903	$849.30	$849.30	$849.30