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	$93.81	5.349%	$98.8279	$98.83	$98.85	$98.80
Purchase #2	$91.42	9.779%	$100.36	$100.36	$100.35	$100.40
Purchase #3	$164.94	10.136%	$181.6583	$181.66	$181.65	$181.70
Purchase #4	$43.39	9.510%	$47.5164	$47.52	$47.50	$47.50
Purchase #5	$106.83	13.599%	$121.3578	$121.36	$121.35	$121.40
Purchase #6	$155.32	8.170%	$168.0096	$168.01	$168.00	$168.00
Purchase #7	$95.32	5.316%	$100.3872	$100.39	$100.40	$100.40
7 purchase totals =	$751.03		$818.1172	$818.13	$818.10	$818.20