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	$43.31	12.120%	$48.5592	$48.56	$48.55	$48.60
Purchase #2	$237.60	10.667%	$262.9448	$262.94	$262.95	$262.90
Purchase #3	$82.68	4.622%	$86.5015	$86.50	$86.50	$86.50
Purchase #4	$39.27	11.780%	$43.896	$43.90	$43.90	$43.90
Purchase #5	$154.52	10.490%	$170.7291	$170.73	$170.75	$170.70
Purchase #6	$209.33	12.302%	$235.0818	$235.08	$235.10	$235.10
Purchase #7	$206.30	7.614%	$222.0077	$222.01	$222.00	$222.00
7 purchase totals =	$973.01		$1,069.7201	$1,069.72	$1,069.75	$1,069.70