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	$140.45	11.518%	$156.627	$156.63	$156.65	$156.60
Purchase #2	$26.54	11.856%	$29.6866	$29.69	$29.70	$29.70
Purchase #3	$111.70	10.685%	$123.6351	$123.64	$123.65	$123.60
Purchase #4	$152.32	3.371%	$157.4547	$157.45	$157.45	$157.50
Purchase #5	$104.95	12.492%	$118.0604	$118.06	$118.05	$118.10
Purchase #6	$149.83	10.560%	$165.652	$165.65	$165.65	$165.70
Purchase #7	$39.89	13.648%	$45.3342	$45.33	$45.35	$45.30
7 purchase totals =	$725.68		$796.4500	$796.45	$796.50	$796.50