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	$230.46	6.286%	$244.9467	$244.95	$244.95	$244.90
Purchase #2	$111.29	11.102%	$123.6454	$123.65	$123.65	$123.60
Purchase #3	$164.76	7.191%	$176.6079	$176.61	$176.60	$176.60
Purchase #4	$24.64	11.125%	$27.3812	$27.38	$27.40	$27.40
Purchase #5	$216.80	6.345%	$230.556	$230.56	$230.55	$230.60
Purchase #6	$196.29	5.746%	$207.5688	$207.57	$207.55	$207.60
Purchase #7	$59.70	13.176%	$67.5661	$67.57	$67.55	$67.60
7 purchase totals =	$1,003.94		$1,078.2721	$1,078.29	$1,078.25	$1,078.30