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	$217.56	8.737%	$236.5682	$236.57	$236.55	$236.60
Purchase #2	$60.89	7.142%	$65.2388	$65.24	$65.25	$65.20
Purchase #3	$158.91	6.222%	$168.7974	$168.80	$168.80	$168.80
Purchase #4	$183.48	6.825%	$196.0025	$196.00	$196.00	$196.00
Purchase #5	$90.96	5.853%	$96.2839	$96.28	$96.30	$96.30
Purchase #6	$155.72	10.759%	$172.4739	$172.47	$172.45	$172.50
Purchase #7	$119.31	12.483%	$134.2035	$134.20	$134.20	$134.20
7 purchase totals =	$986.83		$1,069.5682	$1,069.56	$1,069.55	$1,069.60