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	$48.97	9.305%	$53.5267	$53.53	$53.55	$53.50
Purchase #2	$83.62	6.253%	$88.8488	$88.85	$88.85	$88.80
Purchase #3	$124.78	6.527%	$132.9244	$132.92	$132.90	$132.90
Purchase #4	$123.75	11.856%	$138.4218	$138.42	$138.40	$138.40
Purchase #5	$81.69	11.320%	$90.9373	$90.94	$90.95	$90.90
Purchase #6	$52.87	13.244%	$59.8721	$59.87	$59.85	$59.90
Purchase #7	$121.53	7.861%	$131.0835	$131.08	$131.10	$131.10
7 purchase totals =	$637.21		$695.6146	$695.61	$695.60	$695.50