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	$10.66	4.598%	$11.1501	$11.15	$11.15	$11.20
Purchase #2	$24.42	12.382%	$27.4437	$27.44	$27.45	$27.40
Purchase #3	$55.99	5.509%	$59.0745	$59.07	$59.05	$59.10
Purchase #4	$226.61	6.648%	$241.675	$241.68	$241.70	$241.70
Purchase #5	$140.86	8.268%	$152.5063	$152.51	$152.50	$152.50
Purchase #6	$132.32	11.713%	$147.8186	$147.82	$147.80	$147.80
Purchase #7	$237.55	11.347%	$264.5048	$264.50	$264.50	$264.50
7 purchase totals =	$828.41		$904.1730	$904.17	$904.15	$904.20