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	$236.82	8.496%	$256.9402	$256.94	$256.95	$256.90
Purchase #2	$234.55	10.674%	$259.5859	$259.59	$259.60	$259.60
Purchase #3	$44.72	5.698%	$47.2681	$47.27	$47.25	$47.30
Purchase #4	$131.48	12.167%	$147.4772	$147.48	$147.50	$147.50
Purchase #5	$97.98	5.423%	$103.2935	$103.29	$103.30	$103.30
Purchase #6	$103.32	4.391%	$107.8568	$107.86	$107.85	$107.90
Purchase #7	$184.82	10.438%	$204.1115	$204.11	$204.10	$204.10
7 purchase totals =	$1,033.69		$1,126.5332	$1,126.54	$1,126.55	$1,126.60