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	$109.56	12.836%	$123.6231	$123.62	$123.60	$123.60
Purchase #2	$154.77	4.650%	$161.9668	$161.97	$161.95	$162.00
Purchase #3	$16.32	12.831%	$18.414	$18.41	$18.40	$18.40
Purchase #4	$198.27	10.857%	$219.7962	$219.80	$219.80	$219.80
Purchase #5	$84.33	4.134%	$87.8162	$87.82	$87.80	$87.80
Purchase #6	$68.87	4.815%	$72.1861	$72.19	$72.20	$72.20
Purchase #7	$67.57	7.160%	$72.408	$72.41	$72.40	$72.40
7 purchase totals =	$699.69		$756.2104	$756.22	$756.15	$756.20