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	$165.42	8.184%	$178.958	$178.96	$178.95	$179.00
Purchase #2	$38.89	4.209%	$40.5269	$40.53	$40.55	$40.50
Purchase #3	$216.83	4.869%	$227.3875	$227.39	$227.40	$227.40
Purchase #4	$217.57	12.828%	$245.4799	$245.48	$245.50	$245.50
Purchase #5	$107.59	8.568%	$116.8083	$116.81	$116.80	$116.80
Purchase #6	$160.56	3.192%	$165.6851	$165.69	$165.70	$165.70
Purchase #7	$98.85	5.335%	$104.1236	$104.12	$104.10	$104.10
7 purchase totals =	$1,005.71		$1,078.9693	$1,078.98	$1,079.00	$1,079.00