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	$215.61	10.239%	$237.6863	$237.69	$237.70	$237.70
Purchase #2	$209.86	11.773%	$234.5668	$234.57	$234.55	$234.60
Purchase #3	$76.49	8.746%	$83.1798	$83.18	$83.20	$83.20
Purchase #4	$130.38	4.390%	$136.1037	$136.10	$136.10	$136.10
Purchase #5	$51.92	3.652%	$53.8161	$53.82	$53.80	$53.80
Purchase #6	$99.46	12.419%	$111.8119	$111.81	$111.80	$111.80
Purchase #7	$39.88	13.563%	$45.2889	$45.29	$45.30	$45.30
7 purchase totals =	$823.60		$902.4535	$902.46	$902.45	$902.50