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	$175.57	9.825%	$192.8198	$192.82	$192.80	$192.80
Purchase #2	$177.83	5.420%	$187.4684	$187.47	$187.45	$187.50
Purchase #3	$141.89	12.328%	$159.3822	$159.38	$159.40	$159.40
Purchase #4	$90.39	5.139%	$95.0351	$95.04	$95.05	$95.00
Purchase #5	$40.27	9.488%	$44.0908	$44.09	$44.10	$44.10
Purchase #6	$206.88	10.161%	$227.9011	$227.90	$227.90	$227.90
Purchase #7	$236.32	11.389%	$263.2345	$263.23	$263.25	$263.20
7 purchase totals =	$1,069.15		$1,169.9319	$1,169.93	$1,169.95	$1,169.90