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	$224.35	3.137%	$231.3879	$231.39	$231.40	$231.40
Purchase #2	$219.99	8.222%	$238.0776	$238.08	$238.10	$238.10
Purchase #3	$91.61	3.239%	$94.5772	$94.58	$94.60	$94.60
Purchase #4	$234.37	13.805%	$266.7248	$266.72	$266.70	$266.70
Purchase #5	$18.81	11.292%	$20.934	$20.93	$20.95	$20.90
Purchase #6	$212.56	5.318%	$223.8639	$223.86	$223.85	$223.90
Purchase #7	$10.60	8.231%	$11.4725	$11.47	$11.45	$11.50
7 purchase totals =	$1,012.29		$1,087.0379	$1,087.03	$1,087.05	$1,087.10