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	$193.82	7.578%	$208.5077	$208.51	$208.50	$208.50
Purchase #2	$146.52	12.379%	$164.6577	$164.66	$164.65	$164.70
Purchase #3	$87.68	13.678%	$99.6729	$99.67	$99.65	$99.70
Purchase #4	$162.83	5.394%	$171.6131	$171.61	$171.60	$171.60
Purchase #5	$216.50	11.718%	$241.8695	$241.87	$241.85	$241.90
Purchase #6	$133.38	3.443%	$137.9723	$137.97	$137.95	$138.00
Purchase #7	$45.82	13.428%	$51.9727	$51.97	$51.95	$52.00
7 purchase totals =	$986.55		$1,076.2659	$1,076.26	$1,076.15	$1,076.40