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	$41.51	13.373%	$47.0611	$47.06	$47.05	$47.10
Purchase #2	$91.72	12.327%	$103.0263	$103.03	$103.05	$103.00
Purchase #3	$40.28	9.190%	$43.9817	$43.98	$44.00	$44.00
Purchase #4	$200.73	8.247%	$217.2842	$217.28	$217.30	$217.30
Purchase #5	$217.99	4.533%	$227.8715	$227.87	$227.85	$227.90
Purchase #6	$118.59	10.590%	$131.1487	$131.15	$131.15	$131.10
Purchase #7	$135.83	6.128%	$144.1537	$144.15	$144.15	$144.20
7 purchase totals =	$846.65		$914.5272	$914.52	$914.55	$914.60