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	$150.57	6.853%	$160.8886	$160.89	$160.90	$160.90
Purchase #2	$147.66	13.841%	$168.0976	$168.10	$168.10	$168.10
Purchase #3	$13.50	11.167%	$15.0075	$15.01	$15.00	$15.00
Purchase #4	$203.82	7.348%	$218.7967	$218.80	$218.80	$218.80
Purchase #5	$117.87	5.338%	$124.1619	$124.16	$124.15	$124.20
Purchase #6	$240.35	10.222%	$264.9186	$264.92	$264.90	$264.90
Purchase #7	$125.59	6.373%	$133.5939	$133.59	$133.60	$133.60
7 purchase totals =	$999.36		$1,085.4648	$1,085.47	$1,085.45	$1,085.50