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	$179.52	10.550%	$198.4594	$198.46	$198.45	$198.50
Purchase #2	$20.70	11.654%	$23.1124	$23.11	$23.10	$23.10
Purchase #3	$227.45	12.709%	$256.3566	$256.36	$256.35	$256.40
Purchase #4	$39.29	4.190%	$40.9363	$40.94	$40.95	$40.90
Purchase #5	$153.49	13.131%	$173.6448	$173.64	$173.65	$173.60
Purchase #6	$232.32	8.390%	$251.8116	$251.81	$251.80	$251.80
Purchase #7	$102.87	13.249%	$116.4992	$116.50	$116.50	$116.50
7 purchase totals =	$955.64		$1,060.8203	$1,060.82	$1,060.80	$1,060.80