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	$32.71	8.644%	$35.5375	$35.54	$35.55	$35.50
Purchase #2	$9.29	6.552%	$9.8987	$9.90	$9.90	$9.90
Purchase #3	$42.62	7.472%	$45.8046	$45.80	$45.80	$45.80
Purchase #4	$184.85	6.236%	$196.3772	$196.38	$196.40	$196.40
Purchase #5	$89.98	9.606%	$98.6235	$98.62	$98.60	$98.60
Purchase #6	$120.83	10.103%	$133.0375	$133.04	$133.05	$133.00
Purchase #7	$62.75	4.327%	$65.4652	$65.47	$65.45	$65.50
7 purchase totals =	$543.03		$584.7442	$584.75	$584.75	$584.70