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	$94.64	11.791%	$105.799	$105.80	$105.80	$105.80
Purchase #2	$51.26	4.125%	$53.3745	$53.37	$53.35	$53.40
Purchase #3	$168.94	11.739%	$188.7719	$188.77	$188.75	$188.80
Purchase #4	$123.53	8.232%	$133.699	$133.70	$133.70	$133.70
Purchase #5	$112.85	10.137%	$124.2896	$124.29	$124.30	$124.30
Purchase #6	$185.72	5.679%	$196.267	$196.27	$196.25	$196.30
Purchase #7	$119.95	11.487%	$133.7287	$133.73	$133.75	$133.70
7 purchase totals =	$856.89		$935.9297	$935.93	$935.90	$936.00