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	$150.31	9.190%	$164.1235	$164.12	$164.10	$164.10
Purchase #2	$102.68	8.821%	$111.7374	$111.74	$111.75	$111.70
Purchase #3	$17.87	3.268%	$18.454	$18.45	$18.45	$18.50
Purchase #4	$179.68	11.512%	$200.3648	$200.36	$200.35	$200.40
Purchase #5	$38.81	11.250%	$43.1761	$43.18	$43.20	$43.20
Purchase #6	$86.53	4.561%	$90.4766	$90.48	$90.50	$90.50
Purchase #7	$107.59	8.325%	$116.5469	$116.55	$116.55	$116.50
7 purchase totals =	$683.47		$744.8793	$744.88	$744.90	$744.90