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	$61.35	6.188%	$65.1463	$65.15	$65.15	$65.10
Purchase #2	$163.36	10.761%	$180.9392	$180.94	$180.95	$180.90
Purchase #3	$150.61	3.344%	$155.6464	$155.65	$155.65	$155.60
Purchase #4	$87.32	9.683%	$95.7752	$95.78	$95.80	$95.80
Purchase #5	$54.50	9.294%	$59.5652	$59.57	$59.55	$59.60
Purchase #6	$156.77	10.656%	$173.4754	$173.48	$173.50	$173.50
Purchase #7	$160.69	5.397%	$169.3624	$169.36	$169.35	$169.40
7 purchase totals =	$834.60		$899.9101	$899.93	$899.95	$899.90