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	$234.94	3.825%	$243.9265	$243.93	$243.95	$243.90
Purchase #2	$248.66	13.103%	$281.2419	$281.24	$281.25	$281.20
Purchase #3	$184.83	6.412%	$196.6813	$196.68	$196.70	$196.70
Purchase #4	$38.80	4.273%	$40.4579	$40.46	$40.45	$40.50
Purchase #5	$75.60	7.350%	$81.1566	$81.16	$81.15	$81.20
Purchase #6	$56.90	9.495%	$62.3027	$62.30	$62.30	$62.30
Purchase #7	$143.86	9.865%	$158.0518	$158.05	$158.05	$158.10
7 purchase totals =	$983.59		$1,063.8187	$1,063.82	$1,063.85	$1,063.90