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	$114.60	11.103%	$127.324	$127.32	$127.30	$127.30
Purchase #2	$207.87	10.129%	$228.9252	$228.93	$228.95	$228.90
Purchase #3	$138.95	6.370%	$147.8011	$147.80	$147.80	$147.80
Purchase #4	$199.87	4.325%	$208.5144	$208.51	$208.50	$208.50
Purchase #5	$42.73	8.549%	$46.383	$46.38	$46.40	$46.40
Purchase #6	$156.94	7.634%	$168.9208	$168.92	$168.90	$168.90
Purchase #7	$96.52	7.125%	$103.3971	$103.40	$103.40	$103.40
7 purchase totals =	$957.48		$1,031.2656	$1,031.26	$1,031.25	$1,031.20