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	$99.82	13.365%	$113.1609	$113.16	$113.15	$113.20
Purchase #2	$103.35	8.254%	$111.8805	$111.88	$111.90	$111.90
Purchase #3	$7.33	3.369%	$7.5769	$7.58	$7.60	$7.60
Purchase #4	$17.27	6.547%	$18.4007	$18.40	$18.40	$18.40
Purchase #5	$121.86	10.574%	$134.7455	$134.75	$134.75	$134.70
Purchase #6	$15.34	13.226%	$17.3689	$17.37	$17.35	$17.40
Purchase #7	$184.74	5.491%	$194.8841	$194.88	$194.90	$194.90
7 purchase totals =	$549.71		$598.0175	$598.02	$598.05	$598.10