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	$81.42	11.177%	$90.5203	$90.52	$90.50	$90.50
Purchase #2	$17.71	9.534%	$19.3985	$19.40	$19.40	$19.40
Purchase #3	$33.53	6.225%	$35.6172	$35.62	$35.60	$35.60
Purchase #4	$98.41	12.872%	$111.0773	$111.08	$111.10	$111.10
Purchase #5	$13.37	12.280%	$15.0118	$15.01	$15.00	$15.00
Purchase #6	$211.51	7.594%	$227.5721	$227.57	$227.55	$227.60
Purchase #7	$110.35	13.204%	$124.9206	$124.92	$124.90	$124.90
7 purchase totals =	$566.30		$624.1178	$624.12	$624.05	$624.10