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	$73.59	10.662%	$81.4362	$81.44	$81.45	$81.40
Purchase #2	$130.36	10.107%	$143.5355	$143.54	$143.55	$143.50
Purchase #3	$141.37	9.545%	$154.8638	$154.86	$154.85	$154.90
Purchase #4	$16.50	5.219%	$17.3611	$17.36	$17.35	$17.40
Purchase #5	$68.81	10.596%	$76.1011	$76.10	$76.10	$76.10
Purchase #6	$189.86	3.456%	$196.4216	$196.42	$196.40	$196.40
Purchase #7	$69.30	4.523%	$72.4344	$72.43	$72.45	$72.40
7 purchase totals =	$689.79		$742.1537	$742.15	$742.15	$742.10