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	$128.92	4.272%	$134.4275	$134.43	$134.45	$134.40
Purchase #2	$51.92	5.730%	$54.895	$54.90	$54.90	$54.90
Purchase #3	$43.96	10.165%	$48.4285	$48.43	$48.45	$48.40
Purchase #4	$249.42	10.861%	$276.5095	$276.51	$276.50	$276.50
Purchase #5	$101.99	9.389%	$111.5658	$111.57	$111.55	$111.60
Purchase #6	$37.79	7.406%	$40.5887	$40.59	$40.60	$40.60
Purchase #7	$171.88	8.316%	$186.1735	$186.17	$186.15	$186.20
7 purchase totals =	$785.88		$852.5885	$852.60	$852.60	$852.60