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	$111.41	4.781%	$116.7365	$116.74	$116.75	$116.70
Purchase #2	$80.44	3.357%	$83.1404	$83.14	$83.15	$83.10
Purchase #3	$37.87	5.380%	$39.9074	$39.91	$39.90	$39.90
Purchase #4	$164.76	10.182%	$181.5359	$181.54	$181.55	$181.50
Purchase #5	$132.50	7.491%	$142.4256	$142.43	$142.45	$142.40
Purchase #6	$35.60	11.163%	$39.574	$39.57	$39.55	$39.60
Purchase #7	$197.93	5.223%	$208.2679	$208.27	$208.25	$208.30
7 purchase totals =	$760.51		$811.5877	$811.60	$811.60	$811.50