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	$236.30	8.829%	$257.1629	$257.16	$257.15	$257.20
Purchase #2	$153.87	10.439%	$169.9325	$169.93	$169.95	$169.90
Purchase #3	$54.34	9.687%	$59.6039	$59.60	$59.60	$59.60
Purchase #4	$79.47	9.133%	$86.728	$86.73	$86.75	$86.70
Purchase #5	$156.89	10.595%	$173.5125	$173.51	$173.50	$173.50
Purchase #6	$170.65	11.416%	$190.1314	$190.13	$190.15	$190.10
Purchase #7	$146.72	9.689%	$160.9357	$160.94	$160.95	$160.90
7 purchase totals =	$998.24		$1,098.0069	$1,098.00	$1,098.05	$1,097.90