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	$178.60	4.151%	$186.0137	$186.01	$186.00	$186.00
Purchase #2	$59.46	12.435%	$66.8539	$66.85	$66.85	$66.90
Purchase #3	$221.59	9.621%	$242.9092	$242.91	$242.90	$242.90
Purchase #4	$106.90	5.169%	$112.4257	$112.43	$112.45	$112.40
Purchase #5	$183.48	7.169%	$196.6337	$196.63	$196.65	$196.60
Purchase #6	$217.47	9.742%	$238.6559	$238.66	$238.65	$238.70
Purchase #7	$88.53	10.139%	$97.5061	$97.51	$97.50	$97.50
7 purchase totals =	$1,056.03		$1,140.9982	$1,141.00	$1,141.00	$1,141.00