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	$205.62	10.365%	$226.9325	$226.93	$226.95	$226.90
Purchase #2	$180.26	5.576%	$190.3113	$190.31	$190.30	$190.30
Purchase #3	$176.30	5.195%	$185.4588	$185.46	$185.45	$185.50
Purchase #4	$37.52	3.809%	$38.9491	$38.95	$38.95	$38.90
Purchase #5	$155.45	4.481%	$162.4157	$162.42	$162.40	$162.40
Purchase #6	$130.87	10.527%	$144.6467	$144.65	$144.65	$144.60
Purchase #7	$210.38	6.845%	$224.7805	$224.78	$224.80	$224.80
7 purchase totals =	$1,096.40		$1,173.4946	$1,173.50	$1,173.50	$1,173.40