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	$81.44	12.799%	$91.8635	$91.86	$91.85	$91.90
Purchase #2	$225.78	13.870%	$257.0957	$257.10	$257.10	$257.10
Purchase #3	$126.73	12.417%	$142.4661	$142.47	$142.45	$142.50
Purchase #4	$151.82	4.691%	$158.9419	$158.94	$158.95	$158.90
Purchase #5	$81.71	13.447%	$92.6975	$92.70	$92.70	$92.70
Purchase #6	$217.69	4.765%	$228.0629	$228.06	$228.05	$228.10
Purchase #7	$175.35	6.784%	$187.2457	$187.25	$187.25	$187.20
7 purchase totals =	$1,060.52		$1,158.3733	$1,158.38	$1,158.35	$1,158.40