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	$126.84	8.434%	$137.5377	$137.54	$137.55	$137.50
Purchase #2	$38.62	7.724%	$41.603	$41.60	$41.60	$41.60
Purchase #3	$23.37	10.307%	$25.7787	$25.78	$25.80	$25.80
Purchase #4	$25.70	6.357%	$27.3337	$27.33	$27.35	$27.30
Purchase #5	$67.55	7.318%	$72.4933	$72.49	$72.50	$72.50
Purchase #6	$85.35	4.807%	$89.4528	$89.45	$89.45	$89.50
Purchase #7	$137.43	11.741%	$153.5657	$153.57	$153.55	$153.60
7 purchase totals =	$504.86		$547.7649	$547.76	$547.80	$547.80