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	$118.25	11.335%	$131.6536	$131.65	$131.65	$131.70
Purchase #2	$134.87	5.613%	$142.4403	$142.44	$142.45	$142.40
Purchase #3	$9.39	12.672%	$10.5799	$10.58	$10.60	$10.60
Purchase #4	$51.97	13.323%	$58.894	$58.89	$58.90	$58.90
Purchase #5	$141.48	7.769%	$152.4716	$152.47	$152.45	$152.50
Purchase #6	$52.84	6.296%	$56.1668	$56.17	$56.15	$56.20
Purchase #7	$193.61	10.385%	$213.7164	$213.72	$213.70	$213.70
7 purchase totals =	$702.41		$765.9226	$765.92	$765.90	$766.00