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	$18.75	11.658%	$20.9359	$20.94	$20.95	$20.90
Purchase #2	$132.57	5.501%	$139.8627	$139.86	$139.85	$139.90
Purchase #3	$48.31	10.341%	$53.3057	$53.31	$53.30	$53.30
Purchase #4	$147.90	11.176%	$164.4293	$164.43	$164.45	$164.40
Purchase #5	$143.86	5.586%	$151.896	$151.90	$151.90	$151.90
Purchase #6	$59.41	13.657%	$67.5236	$67.52	$67.50	$67.50
Purchase #7	$150.31	10.484%	$166.0685	$166.07	$166.05	$166.10
7 purchase totals =	$701.11		$764.0217	$764.03	$764.00	$764.00