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	$224.25	6.135%	$238.0077	$238.01	$238.00	$238.00
Purchase #2	$180.92	4.548%	$189.1482	$189.15	$189.15	$189.10
Purchase #3	$41.38	5.851%	$43.8011	$43.80	$43.80	$43.80
Purchase #4	$173.68	3.146%	$179.144	$179.14	$179.15	$179.10
Purchase #5	$15.45	13.773%	$17.5779	$17.58	$17.60	$17.60
Purchase #6	$71.34	9.714%	$78.27	$78.27	$78.25	$78.30
Purchase #7	$141.27	11.464%	$157.4652	$157.47	$157.45	$157.50
7 purchase totals =	$848.29		$903.4141	$903.42	$903.40	$903.40