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	$160.55	11.366%	$178.7981	$178.80	$178.80	$178.80
Purchase #2	$158.90	8.760%	$172.8196	$172.82	$172.80	$172.80
Purchase #3	$185.89	5.584%	$196.2701	$196.27	$196.25	$196.30
Purchase #4	$79.58	12.797%	$89.7639	$89.76	$89.75	$89.80
Purchase #5	$159.52	11.249%	$177.4644	$177.46	$177.45	$177.50
Purchase #6	$120.90	9.778%	$132.7216	$132.72	$132.70	$132.70
Purchase #7	$108.47	10.442%	$119.7964	$119.80	$119.80	$119.80
7 purchase totals =	$973.81		$1,067.6341	$1,067.63	$1,067.55	$1,067.70