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	$80.61	3.636%	$83.541	$83.54	$83.55	$83.50
Purchase #2	$204.78	11.273%	$227.8648	$227.86	$227.85	$227.90
Purchase #3	$103.51	8.197%	$111.9947	$111.99	$112.00	$112.00
Purchase #4	$214.43	12.624%	$241.4996	$241.50	$241.50	$241.50
Purchase #5	$79.26	11.493%	$88.3694	$88.37	$88.35	$88.40
Purchase #6	$111.85	5.745%	$118.2758	$118.28	$118.30	$118.30
Purchase #7	$188.66	12.837%	$212.8783	$212.88	$212.90	$212.90
7 purchase totals =	$983.10		$1,084.4236	$1,084.42	$1,084.45	$1,084.50