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	$198.38	6.544%	$211.362	$211.36	$211.35	$211.40
Purchase #2	$132.72	8.333%	$143.7796	$143.78	$143.80	$143.80
Purchase #3	$71.29	11.800%	$79.7022	$79.70	$79.70	$79.70
Purchase #4	$151.79	9.267%	$165.8564	$165.86	$165.85	$165.90
Purchase #5	$201.59	4.838%	$211.3429	$211.34	$211.35	$211.30
Purchase #6	$38.37	8.160%	$41.501	$41.50	$41.50	$41.50
Purchase #7	$105.26	5.535%	$111.0861	$111.09	$111.10	$111.10
7 purchase totals =	$899.40		$964.6302	$964.63	$964.65	$964.70