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	$217.37	3.295%	$224.5323	$224.53	$224.55	$224.50
Purchase #2	$232.78	13.617%	$264.4777	$264.48	$264.50	$264.50
Purchase #3	$63.85	5.792%	$67.5482	$67.55	$67.55	$67.50
Purchase #4	$124.96	11.621%	$139.4816	$139.48	$139.50	$139.50
Purchase #5	$118.48	10.448%	$130.8588	$130.86	$130.85	$130.90
Purchase #6	$185.99	10.608%	$205.7198	$205.72	$205.70	$205.70
Purchase #7	$39.32	4.464%	$41.0752	$41.08	$41.10	$41.10
7 purchase totals =	$982.75		$1,073.6936	$1,073.70	$1,073.75	$1,073.70