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	$89.95	5.151%	$94.5833	$94.58	$94.60	$94.60
Purchase #2	$95.27	11.133%	$105.8764	$105.88	$105.90	$105.90
Purchase #3	$56.76	12.278%	$63.729	$63.73	$63.75	$63.70
Purchase #4	$225.61	12.699%	$254.2602	$254.26	$254.25	$254.30
Purchase #5	$141.50	13.120%	$160.0648	$160.06	$160.05	$160.10
Purchase #6	$32.83	6.275%	$34.8901	$34.89	$34.90	$34.90
Purchase #7	$176.86	4.382%	$184.61	$184.61	$184.60	$184.60
7 purchase totals =	$818.78		$898.0138	$898.01	$898.05	$898.10