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	$152.59	4.550%	$159.5328	$159.53	$159.55	$159.50
Purchase #2	$15.38	9.622%	$16.8599	$16.86	$16.85	$16.90
Purchase #3	$126.74	13.577%	$143.9475	$143.95	$143.95	$143.90
Purchase #4	$228.80	11.648%	$255.4506	$255.45	$255.45	$255.50
Purchase #5	$67.60	4.302%	$70.5082	$70.51	$70.50	$70.50
Purchase #6	$241.98	9.650%	$265.3311	$265.33	$265.35	$265.30
Purchase #7	$49.52	8.134%	$53.548	$53.55	$53.55	$53.50
7 purchase totals =	$882.61		$965.1781	$965.18	$965.20	$965.10