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	$148.65	10.505%	$164.2657	$164.27	$164.25	$164.30
Purchase #2	$12.53	8.596%	$13.6071	$13.61	$13.60	$13.60
Purchase #3	$102.49	10.594%	$113.3478	$113.35	$113.35	$113.30
Purchase #4	$233.96	5.763%	$247.4431	$247.44	$247.45	$247.40
Purchase #5	$38.85	9.308%	$42.4662	$42.47	$42.45	$42.50
Purchase #6	$97.48	3.309%	$100.7056	$100.71	$100.70	$100.70
Purchase #7	$34.91	4.260%	$36.3972	$36.40	$36.40	$36.40
7 purchase totals =	$668.87		$718.2327	$718.25	$718.20	$718.20