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	$162.78	13.274%	$184.3874	$184.39	$184.40	$184.40
Purchase #2	$92.42	8.663%	$100.4263	$100.43	$100.45	$100.40
Purchase #3	$166.86	4.634%	$174.5923	$174.59	$174.60	$174.60
Purchase #4	$113.75	13.118%	$128.6717	$128.67	$128.65	$128.70
Purchase #5	$40.46	6.165%	$42.9544	$42.95	$42.95	$43.00
Purchase #6	$190.93	8.667%	$207.4779	$207.48	$207.50	$207.50
Purchase #7	$246.27	5.793%	$260.5364	$260.54	$260.55	$260.50
7 purchase totals =	$1,013.47		$1,099.0464	$1,099.05	$1,099.10	$1,099.10