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	$224.75	13.766%	$255.6891	$255.69	$255.70	$255.70
Purchase #2	$31.86	6.130%	$33.813	$33.81	$33.80	$33.80
Purchase #3	$29.69	6.582%	$31.6442	$31.64	$31.65	$31.60
Purchase #4	$102.40	9.647%	$112.2785	$112.28	$112.30	$112.30
Purchase #5	$108.88	10.137%	$119.9172	$119.92	$119.90	$119.90
Purchase #6	$246.69	11.380%	$274.7633	$274.76	$274.75	$274.80
Purchase #7	$212.88	13.451%	$241.5145	$241.51	$241.50	$241.50
7 purchase totals =	$957.15		$1,069.6198	$1,069.61	$1,069.60	$1,069.60