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	$246.66	11.511%	$275.053	$275.05	$275.05	$275.10
Purchase #2	$130.78	4.738%	$136.9764	$136.98	$137.00	$137.00
Purchase #3	$211.52	3.754%	$219.4605	$219.46	$219.45	$219.50
Purchase #4	$12.61	7.314%	$13.5323	$13.53	$13.55	$13.50
Purchase #5	$59.51	12.333%	$66.8494	$66.85	$66.85	$66.80
Purchase #6	$100.30	5.409%	$105.7252	$105.73	$105.75	$105.70
Purchase #7	$245.27	4.808%	$257.0626	$257.06	$257.05	$257.10
7 purchase totals =	$1,006.65		$1,074.6594	$1,074.66	$1,074.70	$1,074.70