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	$189.52	11.792%	$211.8682	$211.87	$211.85	$211.90
Purchase #2	$196.54	8.380%	$213.0101	$213.01	$213.00	$213.00
Purchase #3	$44.78	7.456%	$48.1188	$48.12	$48.10	$48.10
Purchase #4	$54.60	13.222%	$61.8192	$61.82	$61.80	$61.80
Purchase #5	$241.81	12.254%	$271.4414	$271.44	$271.45	$271.40
Purchase #6	$228.48	11.332%	$254.3714	$254.37	$254.35	$254.40
Purchase #7	$78.68	12.762%	$88.7211	$88.72	$88.70	$88.70
7 purchase totals =	$1,034.41		$1,149.3502	$1,149.35	$1,149.25	$1,149.30