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	$214.89	3.566%	$222.553	$222.55	$222.55	$222.60
Purchase #2	$173.80	9.631%	$190.5387	$190.54	$190.55	$190.50
Purchase #3	$64.61	13.502%	$73.3336	$73.33	$73.35	$73.30
Purchase #4	$192.62	6.545%	$205.227	$205.23	$205.25	$205.20
Purchase #5	$78.68	11.535%	$87.7557	$87.76	$87.75	$87.80
Purchase #6	$69.45	10.779%	$76.936	$76.94	$76.95	$76.90
Purchase #7	$208.42	10.495%	$230.2937	$230.29	$230.30	$230.30
7 purchase totals =	$1,002.47		$1,086.6377	$1,086.64	$1,086.70	$1,086.60