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	$176.89	9.441%	$193.5902	$193.59	$193.60	$193.60
Purchase #2	$173.57	13.112%	$196.3285	$196.33	$196.35	$196.30
Purchase #3	$118.34	7.813%	$127.5859	$127.59	$127.60	$127.60
Purchase #4	$122.26	3.178%	$126.1454	$126.15	$126.15	$126.10
Purchase #5	$41.95	4.310%	$43.758	$43.76	$43.75	$43.80
Purchase #6	$132.81	8.710%	$144.3778	$144.38	$144.40	$144.40
Purchase #7	$6.40	8.520%	$6.9453	$6.95	$6.95	$6.90
7 purchase totals =	$772.22		$838.7311	$838.75	$838.80	$838.70