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	$67.28	9.866%	$73.9178	$73.92	$73.90	$73.90
Purchase #2	$107.87	5.160%	$113.4361	$113.44	$113.45	$113.40
Purchase #3	$50.71	9.335%	$55.4438	$55.44	$55.45	$55.40
Purchase #4	$119.59	10.188%	$131.7738	$131.77	$131.75	$131.80
Purchase #5	$34.60	7.541%	$37.2092	$37.21	$37.20	$37.20
Purchase #6	$57.67	3.226%	$59.5304	$59.53	$59.55	$59.50
Purchase #7	$227.82	8.283%	$246.6903	$246.69	$246.70	$246.70
7 purchase totals =	$665.54		$718.0014	$718.00	$718.00	$717.90