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	$94.61	11.278%	$105.2801	$105.28	$105.30	$105.30
Purchase #2	$96.77	11.194%	$107.6024	$107.60	$107.60	$107.60
Purchase #3	$180.66	8.530%	$196.0703	$196.07	$196.05	$196.10
Purchase #4	$40.99	5.182%	$43.1141	$43.11	$43.10	$43.10
Purchase #5	$218.65	3.322%	$225.9136	$225.91	$225.90	$225.90
Purchase #6	$63.29	11.458%	$70.5418	$70.54	$70.55	$70.50
Purchase #7	$231.60	11.561%	$258.3753	$258.38	$258.40	$258.40
7 purchase totals =	$926.57		$1,006.8976	$1,006.89	$1,006.90	$1,006.90