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	$124.56	5.721%	$131.6861	$131.69	$131.70	$131.70
Purchase #2	$25.64	12.223%	$28.774	$28.77	$28.75	$28.80
Purchase #3	$5.80	11.474%	$6.4655	$6.47	$6.45	$6.50
Purchase #4	$25.88	6.397%	$27.5355	$27.54	$27.55	$27.50
Purchase #5	$86.75	4.576%	$90.7197	$90.72	$90.70	$90.70
Purchase #6	$202.98	4.701%	$212.5221	$212.52	$212.50	$212.50
Purchase #7	$247.31	5.493%	$260.8947	$260.89	$260.90	$260.90
7 purchase totals =	$718.92		$758.5976	$758.60	$758.55	$758.60