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	$231.89	7.492%	$249.2632	$249.26	$249.25	$249.30
Purchase #2	$241.71	7.510%	$259.8624	$259.86	$259.85	$259.90
Purchase #3	$107.55	10.504%	$118.8471	$118.85	$118.85	$118.80
Purchase #4	$219.65	8.708%	$238.7771	$238.78	$238.80	$238.80
Purchase #5	$244.48	11.627%	$272.9057	$272.91	$272.90	$272.90
Purchase #6	$99.47	12.425%	$111.8291	$111.83	$111.85	$111.80
Purchase #7	$164.52	8.464%	$178.445	$178.45	$178.45	$178.40
7 purchase totals =	$1,309.27		$1,429.9296	$1,429.94	$1,429.95	$1,429.90