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	$95.70	7.195%	$102.5856	$102.59	$102.60	$102.60
Purchase #2	$32.89	9.738%	$36.0928	$36.09	$36.10	$36.10
Purchase #3	$24.57	7.537%	$26.4218	$26.42	$26.40	$26.40
Purchase #4	$156.65	5.493%	$165.2548	$165.25	$165.25	$165.30
Purchase #5	$166.90	11.754%	$186.5174	$186.52	$186.50	$186.50
Purchase #6	$150.27	12.377%	$168.8689	$168.87	$168.85	$168.90
Purchase #7	$20.45	3.447%	$21.1549	$21.15	$21.15	$21.20
7 purchase totals =	$647.43		$706.8962	$706.89	$706.85	$707.00