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	$207.52	9.700%	$227.6494	$227.65	$227.65	$227.60
Purchase #2	$126.30	9.302%	$138.0484	$138.05	$138.05	$138.00
Purchase #3	$90.94	10.751%	$100.717	$100.72	$100.70	$100.70
Purchase #4	$148.37	5.178%	$156.0526	$156.05	$156.05	$156.10
Purchase #5	$55.40	4.162%	$57.7057	$57.71	$57.70	$57.70
Purchase #6	$116.96	5.506%	$123.3998	$123.40	$123.40	$123.40
Purchase #7	$28.87	8.412%	$31.2985	$31.30	$31.30	$31.30
7 purchase totals =	$774.36		$834.8714	$834.88	$834.85	$834.80