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	$138.28	9.856%	$151.9089	$151.91	$151.90	$151.90
Purchase #2	$79.60	8.840%	$86.6366	$86.64	$86.65	$86.60
Purchase #3	$60.72	11.474%	$67.687	$67.69	$67.70	$67.70
Purchase #4	$13.32	3.726%	$13.8163	$13.82	$13.80	$13.80
Purchase #5	$228.64	13.660%	$259.8722	$259.87	$259.85	$259.90
Purchase #6	$77.90	6.572%	$83.0196	$83.02	$83.00	$83.00
Purchase #7	$101.90	7.649%	$109.6943	$109.69	$109.70	$109.70
7 purchase totals =	$700.36		$772.6349	$772.64	$772.60	$772.60