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	$174.89	12.254%	$196.321	$196.32	$196.30	$196.30
Purchase #2	$118.28	10.826%	$131.085	$131.09	$131.10	$131.10
Purchase #3	$149.28	4.718%	$156.323	$156.32	$156.30	$156.30
Purchase #4	$85.59	9.656%	$93.8546	$93.85	$93.85	$93.90
Purchase #5	$219.78	13.455%	$249.3514	$249.35	$249.35	$249.40
Purchase #6	$166.56	10.178%	$183.5125	$183.51	$183.50	$183.50
Purchase #7	$112.86	12.265%	$126.7023	$126.70	$126.70	$126.70
7 purchase totals =	$1,027.24		$1,137.1498	$1,137.14	$1,137.10	$1,137.20