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	$133.79	13.643%	$152.043	$152.04	$152.05	$152.00
Purchase #2	$99.75	9.671%	$109.3968	$109.40	$109.40	$109.40
Purchase #3	$245.72	7.386%	$263.8689	$263.87	$263.85	$263.90
Purchase #4	$29.35	10.232%	$32.3531	$32.35	$32.35	$32.40
Purchase #5	$74.73	9.159%	$81.5745	$81.57	$81.55	$81.60
Purchase #6	$164.48	8.573%	$178.5809	$178.58	$178.60	$178.60
Purchase #7	$124.88	13.758%	$142.061	$142.06	$142.05	$142.10
7 purchase totals =	$872.70		$959.8782	$959.87	$959.85	$960.00