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	$179.35	5.306%	$188.8663	$188.87	$188.85	$188.90
Purchase #2	$100.99	11.858%	$112.9654	$112.97	$112.95	$113.00
Purchase #3	$100.70	11.328%	$112.1073	$112.11	$112.10	$112.10
Purchase #4	$114.60	10.669%	$126.8267	$126.83	$126.85	$126.80
Purchase #5	$82.37	8.607%	$89.4596	$89.46	$89.45	$89.50
Purchase #6	$171.57	9.762%	$188.3187	$188.32	$188.30	$188.30
Purchase #7	$227.55	4.572%	$237.9536	$237.95	$237.95	$238.00
7 purchase totals =	$977.13		$1,056.4976	$1,056.51	$1,056.45	$1,056.60