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	$12.89	13.158%	$14.5861	$14.59	$14.60	$14.60
Purchase #2	$145.40	9.456%	$159.149	$159.15	$159.15	$159.10
Purchase #3	$39.55	10.124%	$43.554	$43.55	$43.55	$43.60
Purchase #4	$96.51	3.834%	$100.2102	$100.21	$100.20	$100.20
Purchase #5	$195.67	11.136%	$217.4598	$217.46	$217.45	$217.50
Purchase #6	$103.71	8.609%	$112.6384	$112.64	$112.65	$112.60
Purchase #7	$5.38	6.742%	$5.7427	$5.74	$5.75	$5.70
7 purchase totals =	$599.11		$653.3402	$653.34	$653.35	$653.30