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	$111.49	10.706%	$123.4261	$123.43	$123.45	$123.40
Purchase #2	$114.89	8.691%	$124.8751	$124.88	$124.90	$124.90
Purchase #3	$156.37	7.864%	$168.6669	$168.67	$168.65	$168.70
Purchase #4	$191.99	12.177%	$215.3686	$215.37	$215.35	$215.40
Purchase #5	$61.94	6.613%	$66.0361	$66.04	$66.05	$66.00
Purchase #6	$133.83	7.600%	$144.0011	$144.00	$144.00	$144.00
Purchase #7	$119.76	9.291%	$130.8869	$130.89	$130.90	$130.90
7 purchase totals =	$890.27		$973.2608	$973.28	$973.30	$973.30