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	$137.78	11.475%	$153.5903	$153.59	$153.60	$153.60
Purchase #2	$232.80	12.653%	$262.2562	$262.26	$262.25	$262.30
Purchase #3	$200.41	3.255%	$206.9333	$206.93	$206.95	$206.90
Purchase #4	$82.67	9.174%	$90.2541	$90.25	$90.25	$90.30
Purchase #5	$57.33	8.270%	$62.0712	$62.07	$62.05	$62.10
Purchase #6	$180.87	3.611%	$187.4012	$187.40	$187.40	$187.40
Purchase #7	$47.74	10.531%	$52.7675	$52.77	$52.75	$52.80
7 purchase totals =	$939.60		$1,015.2738	$1,015.27	$1,015.25	$1,015.40