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	$38.54	7.767%	$41.5334	$41.53	$41.55	$41.50
Purchase #2	$183.59	13.766%	$208.863	$208.86	$208.85	$208.90
Purchase #3	$113.32	11.573%	$126.4345	$126.43	$126.45	$126.40
Purchase #4	$112.85	13.784%	$128.4052	$128.41	$128.40	$128.40
Purchase #5	$112.77	9.456%	$123.4335	$123.43	$123.45	$123.40
Purchase #6	$160.45	10.261%	$176.9138	$176.91	$176.90	$176.90
Purchase #7	$105.92	6.849%	$113.1745	$113.17	$113.15	$113.20
7 purchase totals =	$827.44		$918.7579	$918.74	$918.75	$918.70